Pediatric Dermatology Ward Rounds Jayakar Thomas
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Introduction: An Approach to Dermatological Diagnosis1

Medicine is an ever-changing science. Within this science is the specialty of ‘cutaneous medicine’, more popularly known as Dermatology. As new research and clinical experiences broaden one's knowledge, one's awareness in changes in clinical presentation, in diagnostic investigative dermatology, and in drug therapy is required.
It is common experience that readiness to treat is always present. But what is quite evident is that the same enthusiasm is not seen in the readiness to diagnose or to learn to diagnose skin diseases. A systematic approach to dermatological diagnosis is required; and it is only appropriate to accept a schematic approach towards the same when dealing with a child, in the following order:
  • Careful history taking,
  • Astute clinical examination, anda
  • Laboratory investigation when indicated
 
HISTORY-TAKING
The history provides valuable information towards particular dermatoses (e.g. an history of consanguineous marriage may provide a clue to diagnosing an autosomal recessive disorder in the offspring). Most dermatological conditions have a classical history of onset, course, and presentation and this underscores the need to have a reliable informant, preferably the parent to narrate the history of the illness when dealing with children. There is no better example for the combined interaction among the patient, parent, and physician than in pediatric dermatology.
 
CLINICAL EXAMINATION
Many skin diseases can be diagnosed by a thorough physical examination alone. The physical examination should include examination of the nails and areas unavailable for self-examination (e.g. oral mucosa, anogenital area, scalp). Good lighting is essential. Diagnosis requires identification of primary and secondary skin lesions by morphology.
 
PRIMARY SKIN LESIONS
Primary lesions are early skin changes that have not yet undergone natural evolution or change caused by manipulation. These are the best clues to diagnosis.
A macule is flat, variably shaped, discolored, and small (less than 10 mm). A patch is a large macule (more than 10 mm). Examples include freckles, flat moles, tattoos, port-wine stains, and the rashes of rickesttsial infections, rubella, measles, and some allergic drug eruptions.
A papule is a solid, elevated lesion usually less than 10 mm. A plaque is a plateau-like lesion more than 10 mm or a group of confluent papules. Examples include warts, some nevi, psoriasis, syphilitic chancre, lichen planus, some drug eruptions, insect bites, seborrheic and actinic keratoses, some lesions of acne, and skin cancers.
A nodule is a palpable, solid lesion more than 10 mm; it may or may not be elevated. Larger nodules (more than 20 mm) are called tumors. Examples include keratinous cysts, small lipomas, fibromas, erythema nodosum, and some lymphomas and other neoplasms.
A vesicle is a circumscribed, elevated lesion containing serous fluid that is less than 5 mm; if more than 5 mm, it is called a bulla. Vesicles or bullae are commonly caused by primary irritants, allergic contact dermatitis, 2physical trauma, sunburn, insect bites, or viral infections (herpes simplex, varicella, herpes zoster); other causes include drug eruptions, pemphigus, dermatitis herpetiformis, erythema multiforme, epidermolysis bullosa, and pemphigoid.
Pustules are superficial and elevated lesions containing pus. They may result from infection or seropurulent evolution of vesicles or bullae. Some causes are impetigo, acne, folliculitis, furuncles, carbuncles, certain deep fungus infections, hidradenitis suppurativa, kerion, pustular miliaria, and pustular psoriasis of the palms and soles.
Wheals (hives) are transient, elevated lesions caused by localized edema. Wheals are a common allergic reaction, e.g., from drug eruptions, insect stings or bites, or sensitivity to cold, heat, pressure, or sunlight. Larger localized areas of edema in the subcutis are called angioedema.
Purpura is a general term referring to areas of extravasated blood. Petechiae are small circumscribed punctate foci of extravasation, whereas ecchymoses are larger confluent areas of extravasation. The term hematoma refers to an area of massive bleeding into the skin and underlying tissues.
Telangiectasia is dilated superficial blood vessels. They may occur in rosacea, in certain systemic diseases (ataxia-telangiectasia, scleroderma), or in long-term therapy with topical fluorinated corticosteroids; most cases are idiopathic.
 
SECONDARY SKIN LESIONS
Secondary lesions result when primary lesions undergo a natural evolution (e.g. a ruptured vesicle) or are manipulated by the patient (e.g. a scratched vesicle).
Scales are heaped-up particles of horny epithelium. The most common scaling rashes are from psoriasis, seborrheic dermatitis, superficial fungal infections, pityriasis versicolor, pityriasis rosea, and chronic dermatitis of any type.
Crusts (scabs) consist of dried serum, blood, or pus. Crusting occurs in many inflammatory and infectious diseases.
Erosion is focal loss of part or all of the epidermis. It often occurs with herpes viruses and pemphigus.
Ulcers are focal loss of the epidermis and at least part of the dermis. When ulcers result from physical trauma or acute bacterial infection, the cause usually is apparent. Less obvious causes include chronic bacterial and fungal infections, various peripheral vascular diseases and neuropathies, systemic scleroderma, and tumors.
Excoriation is a linear or hollowed-out crusted area caused by scratching, rubbing, or picking.
Lichenification is a thickened skin area with pigmentation and accentuated skin markings. Atopic dermatitis and lichen simplex chronicus (localized scratch dermatitis) typically cause lichenification.
Atrophy manifests as paper-thin, wrinkled skin. It occurs in the aged, in discoid lupus erythematosus, after long-term use of topical potent corticosteroids, and sometimes after burns.
Scars are areas of fibrous tissue that replace normal skin after destruction of some of the dermis. Scars may be caused by burns or cuts and less commonly by diseases (e.g. discoid lupus erythematosus).
The arrangement of lesions may be distinctive. Grouping of tense vesicles in seen in herpes simplex and zoster, with a characteristic linear arrangement in the latter. Annularity (a tendency to form rings) is typical in granuloma annulare, erythema multiforme, fixed drug eruption, dermatophyte infections, some forms of Lyme disease, and secondary syphilis. Linearity is sometimes seen with epidermal nevi, linear scleroderma, and con tact dermatitis. In Koebner's phenomenon (isomorphic reaction), lesions in psoriasis, lichen planus, and flat warts mimic the shape of trauma to the skin (e.g. from scratching, rubbing, or other 3injury). The distribution of lesions in certain dermatoses usually follows some common pattern. Some examples include the following:
Acne: face, chest, back
Atopic dermatitis: antecubital and popliteal fossae
Erythema nodosum: anterior legs
Pityriasis rosea: ‘vest’ area
Psoriasis: extensor surfaces, scalp
 
LABORATORY INVESTIGATION
Biopsy is essential for histological diagnosis of obscure, particularly if chronic, and for lesions suggesting malignancy. A fully developed typical lesion is usually chosen for biopsy, but early lesions are a better choice in vesicular, bullous, or pustular eruptions. The simplest procedure is a punch biopsy, in which a tubular punch (diameter of 2 mm or more) is inserted through to the subcutis and the tissue plug is snipped off at its base. Adequate biopsy of some relatively friable lesions (e.g. seborrheic keratoses) may be obtained by scraping with a sharp curette or shaving with a scalpel. To obtain a larger tissue sample or to biopsy deep dermal or subcutaneous lesions, a wedge of skin is removed and the incision sutured. For most small tumors, diagnosis and cure are achieved with complete excision that includes small borders of normal skin. All pigmented lesions, including nevi, should be excised deeply enough for histological evaluation of depth. Superficial biopsies are often inadequate for histological diagnosis, especially of pigmented lesions or when a mycobacterial or a deep fungal infection is suspected.
Microscopic examination of scrapings helps identify superficial fungal infections. Scales are taken from the active, advancing border of the lesion, covered with 20% potassium hydroxide. Misshapen stubs of broken hairs from a scalp lesion must be examined because normal hairs are not always infected (e.g. in tinea capitis). In dermatophyte infections, primarily hyphae are seen, whereas in tinea versicolor and candidal infections, budding yeast and hyphae are seen.
Culture and antibacterial sensitivity testing are advised for acute bacterial skin infections, but they should not delay treatment. Adequate sampling is essential. For a frankly pustular lesion, a swab sample is sufficient; the swab should be placed immediately in broth culture. In chronic infections (e.g. TB, deep fungi), in which the flora may be mixed and relatively sparse, more ample specimens (including deep biopsy specimens) must be cultured and special media may be needed. Culture of superficial fungal infections is occasionally positive even when the scraping is negative.
Wood's light examination involves viewing the skin in a dark room under ultraviolet light filtered through Wood's glass. Tinea versicolor fluoresces a subtle gold color, and erythrasma fluoresces a bright orange-red. Tinea capitis caused by Microsporum canis and Microsporum audouini fluoresce a light green (most Tinea capitis infections are caused by Trichophyton species, which rarely fluoresce). The earliest clue to a Pseudomonas infection, especially in burns, may be green fluorescence, and the white color under Wood's light.
The Tzanck test is rapid and reliable (in experienced hands) for diagnosing herpes simplex, herpes zoster, and pemphigus. A smear of cellular material is scraped from the base and sides of a vesicle and stained with Leishman, Wright's or Giemsa stain. Multinucleated giant cells are seen in herpes simplex, herpes zoster, and varicella but not in vaccinia. Pemphigus can be diagnosed by finding typical acantholytic cells that have very large nuclei and scant cytoplasm and that are no longer attached to each other.
Viral cultures are more sensitive and easier to interpret than the Tzanck test, and identifications usually can be made within 2 or 3 days. If a viral infection is suspected, vesicle fluid can be put into special transport media for culture at specified medical centers.4
Immunofluorescence tests using fluorescence microscopy are an important aid in diagnosing and managing certain skin diseases. Indirect immunofluorescence tests (evaluation of serum for circulating antibodies) show that the serum of a patient with pemphigus or bullous pemphigoid contains specific antibodies that bind to different areas of the epithelium. In pemphigus, the antibody titer may correlate with the severity of the disease. In direct immunofluorescence tests (evaluation of a patient's skin for in vivo antibody deposition), biopsy specimens of skin of patients with pemphigus, pemphigoid, dermatitis herpetiforms, herpes gestations, SLE, and discoid lupus erythematosus (LE) shoe diagnostic patterns of antibody deposition. The direct immunofluorescence test is more definitive than ordinary histology for diagnosing most of these diseases.
Other special diagnostic methods include patch tests for allergic contact dermatitis, darkfield examination for syphilis, skin scrapings for scabies, and hair counts for alopecia.