Histiocytoid Variant of Sweet Syndrome Associated with Azacitidine and Recurrence upon Rechallenge.

Sweet syndrome was first described in 1964, at which time it was termed acute febrile neutrophilic dermatosis.1 Up to 20% of patients with Sweet syndrome have an associated malignancy, of whom about 85% have a hematologic disorder.2 The hallmark of Sweet syndrome is a nodular and diffuse dermal infiltrate of neutrophils identified on biopsy.3 The mechanism of the syndrome is not completely understood, but it is known to be mediated by neutrophils.4 More than three-quarters of patients have systemic findings, with fever in 50%–80% of patients.3 Many medications have been reported to induce the syndrome; granulocyte colonystimulating factor, antibiotics, and vaccines are most frequently observed.2,5 Although it is predominantly mature neutrophils that infiltrate the dermis, abnormal or immature myeloid cells have also been observed.2 In patients with hematologic disorders, both abnormal neutrophils (leukemia cutis) and mature neutrophils may constitute the dermal infiltrate.2 A pathologic histiocytoid variant of Sweet syndrome has been described, characterized by an infiltrate of immature myeloid cells.6 Azacitidine is an antineoplastic agent that is administered for 7 consecutive days every 28 days to treat adult patients with myelodysplastic syndrome or acute myeloid leukemia (AML) who are not eligible for hematopoietic stem cell transplant.7 Two case reports of azacitidine-associated Sweet syndrome8,9 and one case of histiocytoid Sweet syndrome associated with azacitidine10 were retrieved from a literature search of PubMed, Embase, and MEDLINE. The case described here is notable because the patient experienced 2 episodes of Sweet syndrome while receiving azacitidine, with the recurrent episode (after rechallenge with azacitidine) appearing to be the histiocytoid variant. CASE REPORT