INFECTIONSChapter 1

Bacteria are several types of microscopic or ultramicroscopic single-celled organisms occurring in enormous numbers everywhere in nature. They may be free living, saprophytic or parasitic; some of them are pathogenic to man.

It is an inflammatory condition of the hair follicle with changes localized to the opening on the surface or extending a little underneath. Causes include bacterial, e.g. staphylococcal; fungal e.g. Trichophyton rubrum; physical, e.g. occlusion with polythene; chemical, e.g. mineral oils, tar; and drugs, e.g. topical steroids. The so called Bockhart's impetigo is a chronic staphylococcal folliculitis. Clinically, it presents generally as painless small-sized papules or pustules around the follicles. Remove underlying cause if possible. Bland local application, e.g. 1% gentian violet or brilliant green paint can be used. Topical and systemic antibiotics can also be used.

It presents as an acute necrotic infection of a hair follicle which is commonly seen in adult life particularly in seborrheic individuals and diabetics. Such cases usually carry staphylococci in their noses or perineal regions. Mechanical damage, e.g. friction with collar or belt may determine the site. There is a solitary or multiple, follicular and inflammatory nodules. Soon, the necrotic portion is shed, leaving behind a purplish scar. Tenderness and throbbing is usual. Boils occurring on upper lip or cheek can cause cavernous sinus thrombosis. Treatment includes topical or systemic antibiotics.

It is characterized by ulcers covered by thick crusts. Same bacteria are responsible for it as those of impetigo. Most cases occur in children. Poor hygiene, malnutrition and underlying itchy dermatoses, e.g. scabies and pediculosis are the predisposing factors. Small blisters or pus filled cavities appear on a red base which are readily covered by a thick crust. This crust is removed with great difficulty and the ulcer heals after a few weeks leaving a scar. Commonly affected sites are buttocks, thighs and legs.

When the whole depth of a hair follicle is affected by a subacute or chronic pyogenic infection, it is called Sycosis. It is seen in males only. Beard region is commonly affected and seborrheic dermatitis is a predisposing factor. Original lesion is a swollen, reddish papule/pustule centered by a hair. The lesions generally remain as such or coalesce to form an edematous plaque studded with pustules. It resembles a ripened fig hence the term sycosis. Recurrent episodes of varying duration often occur without cicatrization. In the scarring variety (called lupoid sycosis), the center is an atrophic scar which is surrounded by active papules and pustules. This variety usually affects the chin, preauricular region or scalp. Rarely, axillary or pubic region, lower legs, thighs or arms may be affected. Differential diagnosis includes ringworm (tinea barbae), lupus vulgaris and discoid lupus erythematosus. Subacute forms are relatively easily controlled by topical antibiotics. A steroid-cum-antibiotic topical preparation may be useful. Systemic minocycline and zinc preparations are also helpful.

A contagious superficial infection caused by staphylococcal or streptococcal organisms. Children are most often affected, particularly in summer. It usually complicates an underlying itchy condition, e.g. scabies, pediculosis and miliaria. The so-called pemphigus neonatorum is a form of bullous impetigo seen in infants. There are delicate vesicles principally on exposed parts of the body, e.g. face, hands and knees. These rupture quickly to form golden-yellow or brown crusts. There is gradual, irregular and peripheral extension. Healing occurs without scarring. There are few complications except in the presence of systemic disease or malnutrition. Acute glomerulonephritis may sometimes follow streptococcal impetigo. Differential diagnosis includes seborrheic dermatitis, ringworm, eczema, scabies, pediculosis and pemphigus. Prognosis is mostly good. Topical antibiotic, e.g. neomycin, bacitracin, mupirocin and fusidic acid are used. Usually local applications suffice. Occasionally systemic administration is necessary when cloxacillin or erythromycin should be considered. Crusts must be removed by preparations like starch poultice before applying any local treatment. Underlying dermatosis, e.g. scabies and pediculosis should always be looked for and treated.

It is an inflammation of loose connective tissue particularly subcutis, which may be acute, subacute or chronic. It develops most commonly as a complication of an ulcer but can occur in a healthy skin, especially when lymphatic, renal or hypostatic edema is encountered. Apart from streptococci, cellulitis can also be caused by other bacteria, e.g. Haemophilus influenzae. Erythema, tenderness and swelling, occasionally bullae can occur. Edge is usually not well defined. Without treatment, focal suppuration, hemorrhagic necrosis and gangrene may occur. Appropriate antibiotic and removal of predisposing factors should be considered, wherever required.

There is extensive erythema and peeling of the skin in sheets caused by an epidermolytic toxin produced by exotoxin producing strains of Staph. aureus. The organisms are not necessarily present on skin but may exist in other sites, e.g. nose, throat, conjunctiva; from where skin is affected presumably through blood. Staphylococci often belong to group-II producing epidermolysin and are usually resistant to penicillin. These organisms may also cause impetigo. Infants and young children are mostly affected but it can occur in adults also. Skin becomes erythematous and extremely tender. Sheets of skin peel off resembling a scald (epidermal separation occurs superficially at the level of stratum granulosum). Trunk, circumoral and genital regions are mainly affected. Unilateral conjunctivitis is common. Differential diagnosis includes burns, SJS and TEN or Lyell's disease. SSSS should be treated with oral flucloxacillin and correction of water and electrolyte loss. Bland local applications, e.g. paraffin gauze and good nursing care are required.

Acute meningococcal infection is associated with petechial or purpural eruption on the trunk and limbs due to vasculitis or intravascular coagulopathy. The diagnosis is based on direct microscopy of Gramstained cerebrospinal fluid, blood cultures and culture of cerebrospinal fluid. Treatment is intravenous penicillin or ceftriaxone.

It is an acute cutaneous viral infection, in which one or more groups of vesicles appear on an erythematous and edematous base. The cause is Herpesvirus hominis. Two antigenic types of virus exist: Type I and Type II. It spreads by direct contact or droplet infection. Incubation period is 4–5 days. Over half the cases remain carriers throughout life. Primary infection (herpetic gingivostomatitis) is the commonest. Other manifestations include vulvovaginitis, cervicitis and keratoconjunctivitis. Occasionally viremia causes high fever, encephalitis, hepatitis and widespread herpetic eruption. Recurrent infections are common and are usually precipitated by fever, e.g. malaria and pneumonia, sunlight, menstruation or emotional upsets. In the commonest variety (herpes labialis), clusters of small vesicles occur on circumoral region of face preceded by a tingling sensation. Vesicles dry up and clear usually within a week without scarring. Diagnosis is confirmed by culture of virus from vesicle fluid, examination of paired sera after a period of 1–2 weeks for rise in antibody titre and isolation of virus on electron microscopy or detection of viral antigen by immunofluorescence from the lesions. Spirit and powder are used locally for mild attacks. Acyclovir is used topically or systemically 200 mg five times a day for 5–7 days.

It is an acute painful viral infection of skin characterized by the formation of grouped blisters on a reddish background along the course of a sensory root. It is the same virus as that of chickenpox. Zoster may give rise to chickenpox in susceptible contacts or vice versa. Conditions lowering resistance, e.g. trauma, malignancy and cytotoxic drugs predispose to herpes zoster. Severe pain in the distribution of a nerve root is often the first symptom. Three to four days later, closely grouped papules appear on an erythematous base, in the distribution of one or more contiguous dermatomes. These quickly transform into vesicles and sometimes pustules. Necrosis occurs in elderly patients and healing usually in 2–3 weeks with scarring. Thoracic region is involved in half of the cases, followed by cervical, trigeminal and lumbosacral dermatomes. In Herpes Ophthalmicus, ophthalmic division of the trigeminal nerve is affected which leads to ocular palsies or even blindness if not treated early.

Postherpetic neuralgia is the most serious complication, commonly seen in old age. Pain in the distribution of the affected dermatome is excruciating, intractable and extremely difficult to treat. Problems arise when pain is the sole manifestation. Bed rest, analgesics and local antiseptics are sufficient for mild cases. Acyclovir is prescribed at 800 mg five times a day or valacyclovir 1 g thrice daily for 7–10 days. Hyperimmune gammaglobulin can be used for abnormally susceptible patients. Early ophthalmological opinion should be taken for cases of herpes ophthalmicus. Treatment of postherpetic neuralgia is generally less satisfactory. Drugs, e.g. amitryptyline and doxepin are tried.

Warts are common viral tumors acquired by direct contact. Children are particularly prone but can occur at any age. There are following types:

Usually symptomless cauliflower-like, discrete papules conglomerating into larger masses. Common on back of hands or fingers but can occur anywhere.

Flat-topped, skin colored or grayish-yellow papules, occurring in clusters on face, knees and back of hands. Occasionally show Koebner's phenomenon. Differential diagnosis includes lichen planus.

Finger-like projections seen on face, neck or scalp.

Usually painful, rounded, hyperkeratotic lesions seen on pressure areas of the soles and occasionally on palms. Plantar warts occur singly on, in clusters. They form mosaic patterns. Differential diagnosis includes corns and callosities.

Oral warts can occur at any place in the mouth or lips. These are usually painless until trauma is encountered. Mostly, small and lying discrete, usually solitary or a small number is found at a single time. They are rough and raised in routine settings, but can appear in a variety of shapes as dome-shaped growths (white or pink like the color of surrounding mucosa), flat-topped papules or thick finger-like projections. Oral warts are becoming more common in our community due to an increase in the oral sex during the past decade.

These are venereally acquired and usually seen around mucocutaneous junctions and intertriginous areas as sessile or pedunculated cauliflower-like excrescences. Maceration occurs commonly, resulting in infection and malodour. Differential diagnosis includes condylomata lata (secondary syphilis).

Most warts disappear per se in few months to a couple of years while others are treated with:- Cryotherapy, e.g. Liquid nitrogen, CO₂ snow; lotion for plantar warts; salicylic acid and lactic acid in flexible collodion, CO₂ laser and electrocautery. Curettage is useful for common, plantar and digitate warts.

It is caused by one of the largest viruses known to man and belonging to the pox-group. The disease is acquired by direct contact. Lesions are discrete, pearly white, rounded papules, often multiple with umbilicated centers. Commonly, these are seen on the trunk, face and anogenital region. Individual lesions, on squeezing, yield cheesy material full of viral inclusion bodies. These can be treated with a sharpened wooden probe dipped in phenol or strong tincture iodine.

Dermatophytic infection of scalp is common in children. Species frequently found include Trichophyton violaceum, T. tonsurans, T. mentagrophytes, T. schoenleinii, Microsporum canis and M. gypseum. Infection is confined to the growing hair. There are five types. The clinical picture depends upon the causative fungus.

Gray Patch: There is an asymmetrical, non-scarring, patchy loss of hair with lusterlessness and scaling. Itching is occasional.

Black Dot Type: In this variety, there is non-scarring patchy alopecia showing black dots representing broken stumps of hair. Usually, it is not itchy.

Kerion: Zoophilic fungi often cause pronounced inflammatory reaction. It is characterized by painful boggy swellings with follicular pustules, resulting in loss of hair and scarring.

Favus: It is caused by Trichophyton schoenleinii. Clinically, there are yellow cups surrounding hair, called "scutula" (composed of mycelia and debris). Scalp is erythematous with matting of hair and scarring bald patches. Nails are occasionally affected.

Agminate Folliculitis: In this type, there are pustules with patches of hair loss.

Many topical preparations are available, e.g. broad spectrum imidazole compounds such as bifonazole, clotrimazole and isoconazole. In case of secondary bacterial infection, antibiotics can be used.

A superficial fungal infection of the skin known as T. imbricata or “Tokelau”, is limited to Southwest Polynesia, Melanesia, Southeast Asia, India and Central America. Clinically, the lesions are in the form of whirls or multiple rings.

T. corporis is a superficial fungal infection affecting the glabrous skin of trunk, limbs and non-hairy parts of the face. Infection may involve terminal hair in these areas. Usually Trichophyton species are involved. It starts as itchy, spherical or oval erythematous plaques with overlying scaling. It spreads in a centrifugal manner. The lesion clears from the center, whereas the active margin is erythematous and slightly raised. It gives rise to a ring (annular)-shaped lesion, which gives the disease its characteristic name. Different configurations such as a “flower petal” pattern may be observed when multiple lesions coalesce. Adults taking care of children affected with T. capitis (usually the black dot type), may get infected with T. corporis. When there is widespread involvement, it should raise the possibility of an underlying immunocompromised state, for example, HIV infection or diabetes mellitus. Differential diagnosis includes psoriasis, seborrheic dermatitis, pityriasis rosea, nummular eczema and impetigo.

T. corporis, often acquired from infected pet animals, is usually extremely pruritic. Athletes especially wrestlers, who have a close intimate contact, can suffer from outbreaks. In such cases, it is called T. corporis gladiatorum. Most of them are caused by T. tonsurans.

The causative organism is a dermatophyte, which normally lives on the superficial skin surface, and when there is an opportunity, it produces the infection. It can also spread through direct contact with an affected person. Humans can also get the infection from animals (especially pet animals like dogs, cats). Sometimes, it is contracted from other animals like cows, horses, pigs, etc. This infection can be acquired by contact with inanimate objects like contaminated combs, hair brushes, bed linen, etc.

Once Tinea infection is suspected, the skin should be thoroughly examined and fungal scrapings should be taken. Characteristic segmented hyphae and arthrospores are seen under the microscope, after preparing a KOH mount. For this purpose, material should be obtained from the active margin of the lesion. For confirmation of diagnosis, Sabouraud's medium can be used for cultures. The fungus generally grows slowly, taking several days to show results.

Tinea corporis usually responds well to the daily application of topical antifungals. Topical nystatin is ineffective due to its inactivity against dermatophytes. For individuals with extensive cases or patients who are severely immunocompromized, a systemic agent may be preferable. Systemic therapy is also appropriate in patients who have failed to respond to topical therapy. Appropriate systemic agents include oral terbinafine, fluconazole and itraconazole; all of these agents appear to have greater efficacy and fewer side effects than oral griseofulvin. Reasonable regimens in adults include: terbinafine 250 mg daily for one to two weeks; fluconazole 150 mg once weekly for two to four weeks; itraconazole 200 mg daily for one to two weeks; griseofulvin 250 mg three times daily for two weeks.

Onychomycosis (ringworm of the nail, Tinea Unguium) is a dermatophytic infection affecting the nail. It is the commonest nail disease and almost half of the nail diseases are due to fungus. It can affect both the finger- and toenails, but infections of the toenails are usually commonly seen. In the adult population, 6–8% prevalence has been noted. A few or all finger- and toenails become discolored, thickened and friable with debris accumulating under their free edges. Four classical types of onychomycosis have been described: Distal subungual onychomycosis (DSO) is the commonest variety, mostly due to Trichophyton rubrum, which affects the nail bed and the hyponychium. White superficial onychomycosis (WSO) is characterized by the formation of white islands on the plate due to fungal infection of its superficial layers. It is not a common disease, it accounting for only 10% cases of onychomycosis. Sometimes, “keratin granulations”, produced by the nail polish can give rise to a chalky white discoloration. The diagnosis should be confirmed by laboratory tests.

Tinea cruris is dermatophytic infection of the groins. Trichophyton rubrum and Epidermophyton floccosum are the main causative organisms. Males are commonly affected, mainly adults. Transmission is by infected clothes and towels. Symmetrically spreading erythematous and scaly patches with papular or vesicular edges are seen. Sites of involvement are thighs, perineum, perianal region and scrotum. The patient often gets infection from his/ her own tinea pedis or tinea unguium, usually following an exercise leading to profuse sweating. Obesity, diabetes and immunodeficiency predispose to this fungal infection. Diseases to be included in the differentials include erythrasma, seborrheic dermatitis, candidal intertrigo and psoriasis. Lab investigation can confirm the diagnosis. A candidal infection is characterized by the satellite lesions. A KOH preparation would easily yield hyphae, pseudohyphae, or yeast. A coral red fluorescence on Wood's lamp examination confirms the presence of erythrasma. In cases of seborrheic dermatitis or psoriasis, similar lesions at other sites help in the final diagnosis.

Fungal infection of the hand is called Tinea manum. The symptoms are generally severe as compared to T. pedis. There is marked itching and burning along with dryness and fissuring at times.

Tinea pedis also known as Athlete's foot, is the fungal infection of feet, often associated with dermatophyte infection of the hands, nails or groin.

Treatment of T. pedis includes topical as well as oral antifungals. Interdigital infection mostly clears with one week application of a topical antifungal cream. Those suffering from extensive infection, may need oral therapy which may be given in the form of terbinafine 250 mg/ day for 02 weeks, itraconazole 400 mg/ day for 01 week, fluconazole 150 mg weekly for 4–6 weeks. If there is nail involvement, it is a further indication for oral antifungal therapy. Oral antibiotics are required for secondary bacterial infections. Other supportive treatments include the use of talcum powder to combat maceration, treating the footwear with antifungal powders, and avoidance of wearing closed shoes.

Tinea versicolor (Pityriasis Versicolor) is a type of fungal infection, usually caused by a yeast that is a natural inhabitant of the skin. Any one of these conditions can precipitate this infection: sweating, hot climate, oily skin and immunodeficiency. Because the causative organism lives naturally on the skin, this infection is not contagious. People of any type of skin color can be infected with this yeast, mostly in their teens or young adult life. The disease may manifest as: white, pink, red, or brown patches that may be lighter or darker than the surrounding skin. These patches usually occur on the upper half of body including the neck, front and back of chest, and arms. A fluorescent yellow-green color will appear when examined under Wood's lamp. Treatment consists of topical antifungals, which are available as cream, lotion, foam, soap or shampoo. Oral antifungal drugs can also be given to treat severe infection.

Mycetoma is a chronic, localized deep infection. The causative organisms are various species of actinomycetes or fungi. The skin of feet along with its subcutaneous tissues, sometimes even upto the bones, is damaged and there is a discharge of grains from the draining sinuses. Actinomycetoma is the bacterial form, while Eumycetoma is caused by fungi. Grains consist of collections of the microorganisms. It was initially named Madura foot, because it was identified in Madura which is a town in India. Most commonly affected areas are the foot or lower leg, mostly the forefoot at its dorsal aspect. This infection usually occurs in villagers, often farmers or shepherds. The treatment consists of an antibiotic or antifungal which should be tried initially because it may have to be followed by surgery, especially when eumycetoma is present on the extremities. Localized lesions can be best excised, while a surgical de-bulking of the larger lesions can help improve the response to oral therapy.

Chromoblastomycosis is a chronic, long lasting subcutaneous fungal infection. People in the rural areas of tropical or subtropical climates are the usual victims. Many types of fungal organisms are implicated as the cause, which get an entry into the skin through splinters or thorns. The disease has a slowly progressive nature but is rarely fatal with a good prognosis. It is very difficult to cure Chromoblastomycosis. Various therapeutic options are itraconazole either alone or with flucytosine, terbinafine, amphotericin B and cryosurgery with liquid nitrogen.

Candidiasis (Candidosis) is infection of the skin and mucous membranes by yeasts of the genus Candida. Most often the mucous membrane involvement shows up as a thick, white, curdy material covering the glossal, labial or buccal mucosa. There is consequently altered taste sensation and a feeling of soreness. In cases of vaginal candidosis, a similar whitish material may take the form of a discharge from the introitus and involve the adjoining skin. There is itching, burning, and dyspareunia. Prolonged candidal infection can lead to atrophic vaginitis. Cutaneous candidiasis generally involves the folds especially their deepest parts. It presents as brick-red papules and plaques which may be studded with whitish pustules. Small satellite lesions may be seen near the primary infections. It is generally associated with warm, moist environments. An underlying immunocompromized state due to any cause predisposes to candidiasis, such as diabetes mellitus, Cushing's disease, various polyendocrinopathies, anticancer chemotherapy, HIV/AIDS, etc. Even topical application of steroids for oral aphthosis or oral lichen planus can result in candidiasis. Occasionally deeper infections resulting in septicemia, endocarditis or meningitis may occur.

The various clinical patterns of involvement include two types of acute presentations like pseudomembranous or erythematous, and various chronic forms, such as pseudomembranous, erythematous, atrophic, plaque-like, nodular, angular cheilitis, and median rhomboid glossitis. Integumentary varieties of candidiasis are candida intertrigo, vulvovaginitis, perianal and scrotal candidiasis, napkin candidiasis, and candidal paronychia. Diagnosis of candida requires microscopy of smears from the affected area which yields yeasts and filaments, due to pseudohyphae or true hyphae.

Treatment involves removal of the microenvironment conducive to candidal overgrowth. This may require control of diabetes, reduction in serum cortisol levels if high, removal of dentures or other prosthetic devices, or institution of HAART therapy in patients with HIV/ AIDS. Candidal infections respond to topical nystatin or miconazole, clotrimazole, isoconazole, voriconazole, etc. If recalcitrant and in immunocompromized patients, oral fluconazole or itraconazole may be needed. In chronic mucocutaneous candidiasis, intravenous amphotericin B or flucytosine can be used.

The common presentations of cutaneous tuberculosis are:

It is a slowly progressive, chronic tuberculosis of skin affecting people with a good immunity, and is characterized by the formation of caseous nodules. Mycobacterium tuberculosis gains access to the skin by direct inoculation, extension from underlying tuberculous glands or joints, lymphatic spread and hematogenously (rare). Tubercles are seen in upper dermis, composed of a focus of epithelioid cells with interspersed Langhans' giant cells and a peripheral rim of lymphocytes. There is a variable amount of perivascular infiltrate. Center of tubercle may undergo caseation necrosis or even calcify and ultimately fibrosis occurs. Initial lesion is a dusky red plaque which on diascopy (pressure with a glass slide), shows discrete, small, translucent nodules. These nodules are areas of caseation and due to their softness, can be penetrated by match stick. They are called "apple jelly" nodules because of their resemblance to it. Plaque spreads peripherally, with or without ulceration but with scarring. Destruction of underlying cartilage and mucosa can occur. Nose, eyelids, ears and mouth are usually affected. In long standing cases, squamous cell carcinoma may develop. Differential diagnosis includes psoriasis, sarcoidosis, discoid lupus erythematosus, leprosy, tertiary syphilis and leishmaniasis.

Tuberculosis cutis colliquativa is the other name for this tuberculous infection. It arises as a direct extension from an underlying tuberculous focus, e.g. lymph node, bone or joint. Initial lesion is a bluishred nodule which breaks down to form undermined ulcers and fistulae. Edges are undermined, inverted, with dissecting subcutaneous pockets alternating with soft, fluctuating infiltrates and bridging scars. Usually occurs in the parotid, submandibular and supraclavicular regions; lateral neck.

It is a rare form (1–2%) of cutaneous tuberculosis caused by hematogenous dissemination. “Metastatic tuberculous abscess” and “Metastatic tuberculous ulcer” are the synonyms of this condition. It is characterized histologically by the widespread caseation necrosis. It is the result of a hematogenous dissemination of tuberculous organisms from a primary lesion, leading to nodules which are erythematous, non-tender and firm in consistency. Later on, these nodules ulcerate, forming sinuses. Usual clinical presentation is either a fluctuant swelling or a firm subcutaneous nodule. In most of the cases, extremities are mainly affected as compared to the trunk. The skin slowly breaks down to give rise to an undermined ulcer/ sinuses. Rarely, secondary lesions may be seen, especially along the draining lymphatics. Lesions may be multiple in malnourished children. Diagnosis is confirmed by culture. Clinically, it is difficult to differentiate from atypical mycobacterial infection and subcutaneous fungal infections, syphilitic gumma and pyoderma gangrenosum. It should be confirmed by histopathology and culture.

It is a slow growing, verrucous type of tuberculosis, affecting the skin of an already infected person, with a good immunity. Infection can occur due to occupational exposure as seen in butchers, physicians, pathologists and postmortem attendants. In children and young adults, buttocks and legs may be affected by sitting and playing in contaminated streets. Initial lesion is a small, symptomless, purplish-red, indurated warty papule. It extends peripherally in a serpiginous fashion. Center may clear forming a scar or entire lesion may transform into a big warty mass. At times, crusting, exudation or pus may be seen. Differential diagnosis includes lichen planus hypertrophicus, tertiary syphilis, iodo- and bromoderma.

Health of the patient should be improved by better nutrition and healthy environment. Intercurrent infection should be treated and any underlying disease, e.g. diabetes mellitus should be managed properly. In drug therapy, same principles are involved in treating cutaneous tuberculosis as that of any other organ. A combination of drugs should be used, keeping in mind the sensitivity and resistance of the Mycobacterium tuberculosis in a given area. The drugs and their daily dosages are: Rifampicin 450–600 mg, INH 300 mg, Ethambutol 0.7–l g, Pyrazinamide 1.5–2 g. Treatment is usually carried out with four drugs for 2 months and then two drugs for a total of 6 to 12 months.

These include skin lesions of various types in patients with a tuberculous focus elsewhere in the body. Tubercle bacillus cannot be isolated from the skin.

It is a condition in which there is a crop of dusky-red necrotizing papules healing spontaneously to leave pigmented scars. Commonly affects hands, feet, arms, elbows, shoulders, legs and face. Fresh eruptions may continue to appear for months or years.

It is common in young children or adolescents. Minute, skin colored or red, grouped, lichenoid papules appear, giving rise to a permanent goose skin appearance. Papules may be covered by small scales or spines, or occasionally pustules. Eruption persists for months and then involutes without scarring.

Mycobacterium marinum is an atypical mycobacterial infection which is frequently noticed in swimmers. The natural habitat is unreplenished, heated up water in temperate climates (swimming pools, aquaria, rivers and beaches). The vectors are fresh and salt water fish, snails, shellfish and water flees. Cutaneous lesions appear after 2–3 weeks up to 9 months. The sites of involvement are cooler extremities, i.e. hands, arms, shoulders. It can start as a single nodule or pustule which changes into ulcer, abscess and sinuses. The lesions may be multiple in sporotrichoid pattern. It is usually seen in immunocompromized patients. Antibiotics like sulphamethoxazole + trimethoprim, minocycline, doxycycline, rifampicin + ethambutol, clarithromycim, levofloxacin or amikacin can be given for a duration of 14 weeks or longer.

It is a chronic infection caused by a spirochaete called Treponema pallidum, capable of penetrating skin and mucosa and is principally acquired by sexual contact. Occasionally, it is caused by handling infected material or blood transfusion. There is also a congenital form. It is customary to divide acquired syphilis into three stages, i.e. primary, secondary and tertiary.

Primary Syphilis is characterized by the formation of a chancre 10–30 days after the infection associated with regional lymphadenopathy. Chancre is typically a painless indurated ulcer with sharp margins and a smooth glazed surface. In men, it is located on coronal sulcus, glans penis, shaft of penis or the inner surface of prepuce and in women on vulva, vagina or cervix uteri. Extragenital chancre occurs on lips, tongue, tonsils, eyelids, fingers, nipples or perianal region. It heals without treatment in 3–8 weeks, leaving a thin atrophic scar. Differential diagnosis includes chancroid, scabies, herpes genitalis, lichen planus, carcinoma of penis, drug eruptions, lymphogranuloma venereum and traumatic ulcer. Diagnosis is confirmed by dark ground microscopic examination of serum taken from the chancre for the presence of treponema. Serological tests for syphilis, e.g. VDRL, are useless at this stage.

Secondary Syphilis is characterized by the appearance, 6–8 weeks after the primary chancre, of generalized skin eruptions (syphilides) which occur as recurrent and polymorphic lesions (macular, papular or pustular), never bullous or itchy as a rule. Macular syphilides are the first to appear, affecting the trunk, face, limbs, and soles. Lesions are rose colored hence called roseola and on fading leave depigmentation particularly around the neck (necklace of Venus). Papular eruption is deeply infiltrated and dull red in color which may assume annular or circinate shape.

Intramuscular penicillin is still the mainstay of treatment in all forms of the disease. Procaine penicillin 600,000 units are given daily for 10–14 days, or Procaine penicillin G in oil with 2% aluminum monostearate (PAM) 4.8 mega units is administered, or benzathine penicillin in a single dose of 2.4 mega units, is the treatment given in early syphilis. In those who are sensitive to penicillin, erythromycin 500 mg four times a day for 2 weeks or tetracycline 750 mg four times a day for 2 weeks, can be given. In syphilis of more than one year duration, a longer treatment is required, e.g. weekly injections of 2.4 mega units of benzathine penicillin for 3 weeks. Similarly, erythromycin and tetracycline are given for one month in a dose of 500 mg QID. In congenital syphilis, only one dose of benzathine penicillin 50,000 units per kg body weight is given. Pregnant ladies with syphilis should be treated early to prevent or minimize fetal involvement.

It is a chronic infection characterized by constitutional symptoms and matted inguinal lymphadenopathy, i.e. inguinal buboes which ulcerate. The causative agent is Chlamydia trachomatis. Incubation period is 3–20 days. Lymphadenopathy, above and below the inguinal ligament, results in the groove sign. Primary rectal involvement may lead to stricture formation. Elephantiasis of the female genitalia with chronic ulceration and scarring of vulva (esthiomene) may occur. Scarring and lymphedema in males may result in saxophone penis. Cutaneous manifestations include erythema multiforme, erythema nodosum, photosensitivity and scarlatiniform eruption. Pyrexia, weight loss, anemia, arthritis, colitis, glossitis, conjunctivitis, meningitis and pneumonia are other systemic manifestations. Complement fixation test becomes positive after four weeks. Treatment consists of doxycycline 100 mg two times daily or erythromycin 500 mg QID for 3 weeks. Incision and drainage or needle aspiration may be required to treat the abscesses. In complicated cases, help of a surgeon may be needed for colostomy for rectal obstruction, dilatation of the rectal stricture, or repair of rectovaginal fistulae.

Leprosy is a contagious infection, which runs a chronic course. Primary affected organs are the peripheral nerves while skin and mucous membranes of the mouth and upper respiratory tract are secondarily involved, along with the eyes, bones, reticuloendothelial system and testes. The causative agent is Mycobacterium leprae (discovered by Hansen in 1873). Spread depends upon prolonged contact and high genetic susceptibility. There are four types depending upon immunity against the Mycobacterium leprae.

This variety occupies middle position between tuberculoid and lepromatous types. Depending upon the degree of immunity, it may be borderline tuberculoid (BT), mid-borderline (BB) or borderline lepromatous (BL). Accordingly, BT gives a positive lepromin test while it is negative in BL. Clinical features depend upon the type. Nerves and skin are the only tissues directly involved. Skin lesions consist of erythematous macules and plaques. Annular lesions are common with a band of well-defined erythema surrounding a hypopigmented center.

It is a type with transitional immune status. Lepromin test is unpredictable. Nerves and skin are involved. Cutaneous lesions comprise of asymmetrical, nondescript macules. Diagnostic tests include skin smear for M. leprae, histopathology of a biopsy specimen from skin or nerve and Lepromin test. Differential diagnosis includes pityriasis alba, lupus vulgaris, discoid lupus erythematosus, drug eruption, guttate psoriasis, granuloma annulare and sarcoidosis.

The tissues directly affected are only nerves and skin. Cutaneous lesions consist of erythematous, pigmented or hypopigmented macules which are dry, anesthetic and anhidrotic. Edges are raised and well-defined. Nerves are thickened with associated anesthesia and muscle weakness. Ulnar, peroneal and greater auricular nerves are palpably thickened. Eye damage is due to involvement of trigeminal and facial nerves. There is resorption of distal bones of hands and feet with associated trophic ulceration of skin. In this type, lepromin test is positive (denoting high immunity). Bacilli are few in number.

Cutaneous changes are the first to appear, showing bilaterally symmetrical eruption of slightly hypopigmented macules, papules, plaques and nodules. There is predilection for face, limbs and buttocks. Hair growth and sensation remain intact. Later changes include ulceration of nasal and buccal mucosa and other parts of the body, diffuse thickening of skin (leonine facies), ophthalmic damage, testicular atrophy, gynecomastia, absorption of bone and late stage peripheral nerve damage. In this type, lepromin test is negative (denoting no immunity). Bacilli are found in large numbers. Acute reactions may follow treatment particularly with dapsone. Such reactions, seen in lepromatous leprosy, may be precipitated by stress, intercurrent infection, pregnancy or injury. Either the existing lesions may become prominent (Type I) or erythema nodosum leprosum (Type II) may be seen.

Help of plastic surgeon, orthopedic surgeon and physiotherapist is sometimes required for disfiguring lesions and paralyzed muscles, etc.

Advise the patient to elevate the living standards and improve public health education.

Treatment is done mainly on outpatient basis. Hospitalization is necessary only for patients with reactions, side effects of drugs or for surgical treatment of complications. With emergence of resistance against drugs, e.g. dapsone, rifampicin, clofazimine and ethionamide, WHO has recommended multiple drug treatment (MDT). Number of drugs used and length of treatment varies according to the type of leprosy as follows:

Anti-leprosy drug therapy is maintained in full dosage. Type I reaction requires 40–80 mg prednisolone daily with gradual reduction over 4–9 months. Type II reactions are treated with bed rest, analgesics and prednisolone 60 mg daily with rapid tapering over a month. Alternatively, thalidomide 100 mg thrice daily, or clofazimine 300 mg daily, may be used. Pain in the motor nerves can be relieved by intraneural injection of a mixture of hyaluronidase 1500 units, 1 ml of 2% lignocaine and 1 ml of hydrocortisone suspension (25 mg/ml) given with a size 14 needle. Iridocyclitis is treated with 1% hydrocortisone eye drops and mydriatics, e.g. 1% atropine.

Scabies is a contagious parasitic disorder often occurring in epidemics. It is caused by a minute mite, i.e. Sarcoptes (Acarus) scabiei. Fertilized females burrow into the skin laying eggs which after hatching moult three times to become adults. Cycle is repeated every 14–17 days. The disease affects all ages and both sexes. Severe itching occurs, usually nocturnal in character. More than one family member is often affected by sleeping together. Latent period before itching develops is 2–6 weeks. Characteristic lesions are burrows which are grayish linear, C-shaped or S-shaped, slightly raised lesions seen in typical sites, e.g. interdigital clefts, ulnar border of hands, wrists, elbows, axillae, umbilicus, buttocks, penis, breasts and nipples. Palms and soles of feet are affected in infants. Face is usually not affected except in children. Penile lesions look like blind boils. Discrete papules, vesicles and pustules appear secondarily and dominate the clinical picture. Less commonly, Norwegian (crusted) scabies, seen in immunocompromised patients, is characterized by heavy scaling and crusting harbouring numerous mites. Itching may not be pronounced. Complications include secondary infection, e.g. impetigo, boils and ecthyma, eczematization particularly in infants and persistent itchy post-scabetic nodules. Diagnosis is confirmed by scraping a burrow with a scalpel, putting a small amount of KOH 10% solution and finally looking under the microscope for the acarus or the eggs. Nocturnal itching and involvement of more than one family members is very suggestive.

There should be treatment of the patient and all other inmates of the house whether itching or not. The topical preparation should be applied on whole body below collar line (entire body in infants). Laundering of clothes should be done and no special disinfection is required. Scabies should be treated first and complications later. Medicaments used are: 25% benzyl benzoate emulsion (12.5% for children below seven), 1% gamma benzene hexachloride cream and lotion, 10% sulphur ointment (2.5% for infants), 25% monosulfiram lotion, 10% crotamiton cream, 0.5% malathion lotion, 5% permethrin cream and lotion. Single oral dose of Ivermectin, 200 mg/ kg can be given and may be repeated weekly twice or thrice.

It is almost confined to scalp but rarely invades beard or exceptionally other hairy areas. Density of population is usually highest in the occipital and preauricular regions. Infestation occurs by combs and shared head gear. Long hair and infrequent washing increase susceptibility. Women and children are commonly affected. Itching is most marked around the occipital region and sides of scalp. Secondary infection with suboccipital adenitis is common and may be the presenting complaint. Nits on the occipital region resemble scales. Hair may be matted together with pus, producing foul odour. Diagnosis is confirmed by the presence of lice or nits.

1% gamma benzene hexachloride cream and lotion, 5% permethrin cream and lotion, 0.5% carbaryl lotion, 0.5% malathion lotion.

It is an eruption of recurrent pruritic papules, usually grouped and mostly seasonal, typically occurring in young children due to insect bites. Examples of offending insects include fleas, bed bugs, mosquitoes, midges and lice. Papular urticaria is uncommon before the age of two because of lack of sensitivity and after the age of seven due to development of hyposensitization. There are irritable weals, often in clusters, surmounted by papules or occasionally bullae. Recurrent crops lasting two to ten days leave pigmentation. Distribution depends upon the type of insect. Airborne insects often bite on the exposed parts like hands, face, arms, neck and lower legs. Fleas and bed bugs produce lesions mainly on the trunk. Secondary infection is common.

Prevention against insects is most important. Family pets like dogs or cats, or bird's nests may be the source. Spraying of insecticides inside the house is useful. Once the lesions have appeared, 1% phenol or 1% menthol in calamine lotion will be soothing. Oral antihistamines are also useful.

It is also called Lahore sore, Quetta boil, Delhi boil, Mughal sore and oriental sore. There are various species of Leishmania, e.g. L. tropica, L. major, L. aethiopica and L. infantum. Cutaneous leishmaniasis is transmitted by sandflies, e.g. Phlebotomus papatasii and Phlebotomus sergenti in Pakistan. L. major, a zoonosis, is commonly seen in gerbils while L. tropica is primarily a disease of human beings. Two acute forms (wet and dry) and a chronic form (recidivans) are seen.

Sodium stibogluconate (Pentostam) 20 mg/kg intramuscular daily (maximum 850 mg) for 10–20 days. Meglumine antimoniate (Glucantime) 60 mg/kg body weight intramuscular daily (maximum 850 mg) for 10–14 days. Cryotherapy e.g. liquid nitrogen and CO₂ snow can be used locally. Prophylaxis is done by sandfly control measures and immunization with cultures of L. tropica.