By Gary M. White, MD
Acute infiltration of the skin with these bright red plaques.
Sweet's syndrome (SS), also known as acute febrile neutrophilic dermatosis, is a hypersensitivity reaction to a variety of systemic factors that mimics an infection. A myeloproliferative disorder, e.g., myelodysplastic syndrome is sometimes associated.
SS may present with fever, leukocytosis, and rapidly developing painful, red plaques on the upper back, arms, face, neck, or elsewhere. The abdomen, lower back, buttocks, and posterior thighs tend to be spared. The surface of these plaques may exhibit a mammillated appearance, pustules, pseudovesiculation, or crusting. Pathergy may occur. Erythema nodosum-like lesions may occur on the legs and arms. Conjunctivitis, arthralgias, and arthritis may be present. Women are more frequently affected, with the mean age in one study of 53, with a broad incidence peak in the fourth to the seventh decades. Children, however, may also be affected. There is a more chronic form that occurs on the face. A rare giant cellulitis-like Sweet's syndrome occurs. Histiocytoid SS is characterized histologically by an infiltrate of histiocytoid cells. It is similar to classic SS, but extracutaneous involvement has not been reported [JAAD 2015;72;131]. Neutrophilic dermatosis of the dorsal hands is felt to be a variant of SS.
Subcutaneous SS is characterized by a subcutaneous neutrophilic panniculitis and an association with myelodysplasia. Positive criteria found in almost all reported cases include (1) nodules or plaque lesions, (2) systemic symptoms such as fever and malaise, (3) histologic evidence of a subcutaneous lobular neutrophilic infiltrate, (4) association with myelodysplasia, and (5) sensitivity to systemic corticosteroids.
Rarely, internal organs may be involved, e.g., the lung, heart, bone, kidney, liver, and CNS.
A long list of diseases have been associated with and thought to precipitate SS. Respiratory infection preceding the eruption is perhaps most characteristic. Major categories of precipitants include infectious (e.g., tonsillitis, vulvovaginal infections, HIV, coccidioidomycosis, Chlamydia), inflammatory diseases (e.g., inflammatory bowel disease, Crohn's disease, SLE, RA, Sjögren's syndrome), solid carcinomas (e.g., breast, stomach, prostate, colon), and hemoproliferative diseases (e.g., leukemia, myelodysplasia, lymphoma). Miscellaneous precipitants include sarcoidosis, drugs (e.g., leukocyte colony stimulating factor, minocycline, furosemide, granulocyte colony-stimulating factor), and pregnancy.
A throat culture and an ASO are useful to exclude a preceding streptococcal infection. A CBC should be obtained to exclude the possibility of a related myeloproliferative disorder, e.g., acute myelogenous leukemia. A thorough HP, LFT's, creatinine, and urine analysis are also appropriate. An SPEP may be obtained to exclude a paraprotein which occurs slightly more frequently than in the general population.
The standard therapy is prednisone, e.g., 1.0 mg/kg/day. It usually gives dramatic relief of constitutional symptoms within days and clearing of the skin within a week. It should be tapered within 2-4 weeks. As many as one-fourth of patients however will experience a relapse and some will be plagued by chronic, relapsing disease.
Other therapies which have been reported include doxycycline 100 mg BID, cyclosporin (e.g., 4 mg/kg/day), dapsone (e.g., 50-100 mg/day) and colchicine. Potassium iodine can be effective but a severe allergic reaction has been reported and it is best avoided if possible.
Larger lesions may ulcerate.
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