Sweet syndrome, pyoderma gangrenosum, and subcorneal pustular dermatosis are neutrophilic dermatoses – conditions that have an inflammatory infiltrate consisting of mature polymorphonuclear leukocytes. The neutrophils are usually located within the dermis in Sweet syndrome and pyoderma gangrenosum; however, in subcorneal pustular dermatosis, they are found in the upper layers of the epidermis. Sweet syndrome, also referred to as acute febrile neutrophilic dermatosis, is characterized by pyrexia, elevated neutrophil count, painful erythematous cutaneous lesions that have an infiltrate of mature neutrophils typically located in the upper dermis, and prompt clinical improvement following the initiation of systemic corticosteroid therapy. Classical, malignancy-associated, and drug-induced variants of Sweet syndrome exist. Pyoderma gangrenosum is characterized by painful, enlarging necrotic ulcers with bluish undermined borders surrounded by advancing zones of erythema; its clinical variants include: ulcerative or classic, pustular, bullous or atypical, vegetative, peristomal, and drug-induced. Subcorneal pustular dermatosis is an uncommon relapsing symmetric pustular eruption that involves flexural and intertriginous areas; it can be idiopathic or associated with cancer, infections, medications, and systemic diseases. Since Sweet syndrome, pyoderma gangrenosum, and subcorneal pustular dermatosis share not only the same inflammatory cell but also similar associated systemic diseases, it is not surprising that the concurrent or sequential development of these neutrophilic dermatoses has been observed in the same individual. Also, it is not unexpected that several of the effective therapeutic interventions – including systemic drugs, topical agents, and other treatment modalities – for the management of these dermatoses are the same.
The treatment of choice for Sweet syndrome and idiopathic pyoderma gangrenosum is systemic corticosteroids; however, for subcorneal pustular dermatosis, dapsone is the drug of choice. Yet, tumor necrosis factor-α antagonists are becoming the preferred choice when pyoderma gangrenosum is accompanied by inflammatory bowel disease or rheumatoid arthritis. Potassium iodide and colchicine are alternative first-line therapies for Sweet syndrome and indomethacin (indometacin), clofazimine, cyclosporine (ciclosporin), and dapsone are second-line treatments. Cyclosporine is effective in the acute management of pyoderma gangrenosum; however, when tapering the drug, additional systemic agents are necessary for maintaining the clinical response. In some patients with subcorneal pustular dermatosis, systemic corticosteroids may be effective; yet, systemic retinoids (such as etretinate and acitretin) have effectively been used for treating this neutrophilic dermatosis – either as monotherapy or in combination with dapsone or as a component of phototherapy with psoralen andUVAradiation. Topical agents can have an adjuvant role in themanagement of these neutrophilic dermatoses; however, high-potency topical corticosteroids may successfully treat localized manifestations of Sweet syndrome, pyoderma gangrenosum, and subcorneal pustular dermatosis. Intralesional corticosteroid therapy for patients with Sweet syndrome and pyoderma gangrenosum, hyperbaric oxygen and plasmapheresis for patients with pyoderma grangrenosum, and phototherapy for patients with subcorneal pustular dermatosis are other modalities that have been used effectively for treating individuals with these neutrophilic dermatoses.