Myelodysplasia cutis and VEXAS syndrome initially diagnosed as histiocytoid Sweet syndrome: A diagnostic pitfall

Histiocytoid Sweet syndrome (H‐SS) is a histopathological variant of Sweet syndrome (SS) defined by cutaneous infiltration of immature myeloid cells morphologically resembling histiocytes. The association of H‐SS with underlying malignancy, particularly myelodysplastic syndromes, is well‐established. Myelodysplasia cutis (MDS‐cutis) has been proposed to describe cases historically diagnosed as H‐SS but characterized by shared clonality of the myeloid infiltrate in skin and bone marrow. Therefore, identifying patients who might have MDS‐cutis is critical for the management of the associated hematologic malignancy. VEXAS syndrome, an adult‐onset autoinflammatory disease, should also be included in the histopathologic differential diagnosis of H‐SS, as it shares clinical and pathologic features with MDS‐cutis. Through the presentation of two cases, we aim to highlight the defining features and key clinical implications of MDS‐cutis and VEXAS syndrome.