Sweet's syndrome in the setting of CD34-positive acute myelogenous leukemia treated with granulocyte colony stimulating factor: evidence for a clonal neutrophilic dermatosis

Background: Sweet's syndrome in the setting of hematologic dyscrasias can be categorized into paraneoplastic-associated SS, drug-induced SS, and SS with leukemia cutis. Apart from those cases demonstrating concomitant leukemic infiltrates, it has been surmised that SS is a reactive phenomenon induced by a specific cytokine milieu. Methods: The authors present a patient with CD34+ acute myelogenous leukemia (AAML) who developed SS in the setting granulocyte colony stimulating factor (CCSF) therapy, Routine light microscopy and molecular studies were carried on the patient's skin biopsy specimen and post-treatment marrow. An X inactivation assay for clonality was employed. Results: Routine light microscopic examination revealed differentiated myeloid precursors including myelocytes and metamyelocytes within the subcutis; myeloblasts were not identified. In addition, in the overlying skin, features typical of SS were observed. The neutrophils demonstrated dysplastic features including hypolobation compatible with a Pseudo Pelger-Huet anomaly. X inactivation studies showed clonality both within her post-treatment marrow and skin biopsy specimen. Conclusions: Sweet's syndrome developing in CD34+ AML patients following GCSF therapy likely reflects therapy induced differentiation of sequestered leukemic cells, hence indicative of a clonal neutrophilic dermatosis.