Sweet's syndrome associated with clonal hematopoiesis of indeterminate potential responsive to 5-azacitidine

Sweet's syndrome (SS) is a rare condition characterized by the abrupt appearance of painful skin lesions due to neutrophilic dermal infiltration. Hematologic neoplasms, particularly acute myeloid leukemia (AML) and myelodysplastic syndromes (MDSs), have been commonly reported in association with SS. Clonal hematopoiesis of indeterminate potential (CHIP) is an emerging entity that is a precursor state to myeloid neoplasms. CHIP has not been previously associated with SS. We report the case of a 71-year-old man who presented with recurrent, painful edematous and erythematous papules and nodules for 18 months despite treatment with corticosteroids. He had normal blood counts, but a macrocytosis was noted (110 fl). Alternative causes of macrocytosis were ruled out. A skin biopsy confirmed a diagnosis of SS. Bone marrow biopsy specimen yielded a normal karyotype except for loss of the Y chromosome and equivocal morphologic findings. Polymerase chain reaction (PCR) and reverse transcription polymerase chain reaction (RT-PCR) of selected genes from the peripheral blood demonstrated a mixed lineage leukemia (MLL) partial tandem duplication (PTD) and sequence variant in CCAAT/enhancer binding protein alpha (CEBPA). These findings were consistent with a diagnosis of CHIP. The patient was treated with 5-azacitidine and achieved a complete remission of his skin lesions and was able to discontinue corticosteroids. To our knowledge, this is the first report of a patient with recurrent SS associated with CHIP. In addition to other myeloid neoplasms like AML and MDS, CHIP should be considered as a potential etiology in cases of recurrent SS. Treatment with a hypomethylating agents such as azacitidine could also serve as an alternative to systemic corticosteroid therapy.