Background: Sweet syndrome is an acute neutrophilic dermatosis that occurs with malignant diseases, mainly myeloid hemopathies, in about 20% of cases. When associated with myelodysplasia, Sweet syndrome may be clinically atypical. It can be histologically unusual. Concomitant infiltration of mature neutrophils and immature myeloid cells has been reported, and its significance is still debated. In few patients, lymphocytic infiltrates are the presenting feature of Sweet syndrome with myelodysplasia.
Observations: We present 9 male adult patients with chronic Sweet syndrome, all with recurrent eruptions of erythematous and annular plaques that were associated with relapsing polychondritis in 4 of the 9 patients. Results from sequential biopsies showed that infiltrates were initially composed of lymphocytes and that neutrophilic dermal infiltration typical of Sweet syndrome occurred 24 to 96 months later, except in 2 cases. Moreover, atypical mononuclear cells were present on all initial biopsy specimens and strongly reacted to CD68 and myeloperoxidase, indicating a myeloid origin. Myelodysplastic syndrome occurred in all 9 patients, concomitantly with the neutrophilic infiltrate in 4 cases.
Conclusions: Lymphocytic infiltrates with a clinical aspect of Sweet syndrome might represent the initial stage of a cutaneous dysgranulopoiesis syndrome and should lead to the research of atypical myeloid cells in skin infiltrate, blood, and bone marrow for the early detection of an associated myelodysplastic syndrome.