[Differential diagnostic specific skin infiltrates in chronic myelomonocytic leukemia].

A 72-year-old male patient presented with multiple erythematous plaques on the lower arms, lower legs and feet. The patient suffered from rheumatoid arthritis and accompanying interstitial granulomatous dermatitis under treatment with tocilizumab. Several months prior to presentation a chronic myelomonocytic leukemia (CMML) had been diagnosed. The skin biopsy showed a perivascular infiltration of medium-sized cells with positivity for CD123, CD303 and CD4 with a low proliferation activity so that a diagnosis of a CMML-associated proliferation of plasmacytoid dendritic cells was made. The differential diagnosis of specific cutaneous infiltrates in CMML is discussed.