Sweet's syndrome in a patient with acute Crohn's colitis and longstanding ankylosing spondylitis

Acute neutrophilic dermatosis, also referred to as Sweet's syndrome according to the first description in 1964, occurs not only as an isolated phenomenon but also in the context of neoplastic and inflammatory diseases, occasionally including arthritides. Recently Sweet's syndrome has been reported in a small number of patients with chronic inflammatory bowel disease, mostly in advanced stages of the disease. Here, we describe the sudden outbreak of acute neutrophilic dermatosis in coincidence with the onset of severe Crohn's disease (CD) in a patient with long-standing ankylosing spondylitis (AS). This condition has not been described before and therefore Sweet's syndrome should be added to the spectrum of skin manifestations the rheumatologist has to think about in the context of the spondylarthropathies (SpA). Furthermore, this case report is of interest because the skin lesions of Sweet's syndrome are somewhat similar to psoriasis, which is a rather frequent feature of the spondylarthropathies. This article intends to clarify the clinical and histological differentiation between Sweet's syndrome, psoriatic skin lesions and erythema nodosum for the rheumatologist and stresses that these conditions must each be treated in a completely different manner.