Chronic relapsing remitting Sweet syndrome--a harbinger of myelodysplastic syndrome.

Sweet syndrome (SS) is an acute febrile neutrophilic dermatosis. It has been associated with malignant disease, especially acute myeloid leukaemia (AML), infections, autoimmune disorders and drugs, particularly granulocyte colony-stimulating factor (GCSF). No cause is found in the rest, which are labelled idiopathic. We describe 15 patients with SS, which we believe represent 'immune dysregulation' secondary to myelodysplastic syndrome (MDS). We initially identified 31 patients with SS in a cohort of 744 patients with MDS and 215 with AML seen over a 6-year period (2004-10). The cause in 16 patients could be attributed either to administration of GCSF or chemotherapy. The eruption was brief and resolved spontaneously or following withdrawal of GCSF. Fifteen patients however, had a chronic debilitating illness dominated by the skin eruptions. Diagnosis of chronic relapsing SS was delayed because the pathology was not always typical of classical neutrophil-rich SS and included lymphocytic and histiocytoid infiltrates and bone marrow was not always performed because the relevance of the eruption to MDS was often not immediately appreciated. All these patients had 'low risk' MDS, diagnosed at a median of 17 months (range 0-157) following the diagnosis of SS. We describe a chronic debilitating episodic clinically distinctive skin eruption with features of SS but not always definitive histopathology often associated with immunological abnormalities affecting other systems related to underlying low risk MDS.