Sweet's syndrome (acute febrile neutrophilic dermatosis) is a disease characterized by the abrupt onset of red, tender, cutaneous plaques on the face, extremities and upper trunk accompanied by fever, arthralgia or arthritis and neutrophilic leukocytosis. Histologically, there are distinctive, dense, dermal infiltrates of neutrophils. This case report describes a case of Sweet's syndrome characterized by rheumatic onset, microhematuria and subcutaneous nodular lesions on the legs resembling erythema nodosum. The etiopathogenesis and relationship between Sweet's syndrome and infectious and non infectious diseases is discussed. The overlap between this peculiar syndrome and some aspects of inflammatory rheumatic diseases, namely seronegative spondyloarthritides, is suggested.