Necrotizing ulcerative periodontitis (NUP) occurs as a result of extension of necrotizing ulcerative gingivitis (NUG) into the periodontal structures, leading to loss of attachment and bone loss. There are two types of NUP described, on the basis of its relationship to acquired immunodeficiency syndrome (AIDS) following as Non-AIDS type NUP and AIDS-associated NUP. According to American Academy of Periodontology, refractory periodontitis has been defined as those cases, which do not respond to any treatment provided, whatever the thoroughness or frequency. Severe periodontitis has been observed in patients who exhibit either defective numbers of neutrophils or defective neutrophil function. Some of the conditions associated with defective neutrophils are Papillon-Lefévre syndrome, Chédiak-Higashi syndrome, Down syndrome, hypophosphatasia, neutropenia, and leukocyte adhesion deficiency.