Sweet's syndrome with lung involvement. Severe dyspnea and pulmonary infiltrates were associated with recurrent episodes of Sweet's syndrome (acute febrile neutrophilic dermatosis) in a 54-yr-old woman with myelodysplasia. Lung and skin biopsies revealed a sterile infiltration of the interstitial tissues by mature neutrophils. Corticosteroid therapy resulted in rapid clinical improvement; however, recurrent episodes were increasingly resistant to therapy, and she ultimately died from respiratory failure. Sweet's syndrome involving the lung is rare, with only two previously reported cases documented by lung biopsy. Prompt recognition of Sweet's syndrome with lung involvement is important because of the potential for severe respiratory compromise. 