Targeting T cells to hit B cells: successful treatment of cutaneous plasmacytosis with topical pimecrolimus.

Cutaneous plasmacytosis is a rare disease predominantly found in Japanese patients. We describe the case of a 75-year-old white female with cutaneous plasmacytosis of the face and involvement of the bone marrow. In contrast to other cases of cutaneous plasmacytosis, the patient revealed hypogammaglobulinemia and elevated levels of free light chains in the urine. Treatment with topical pimecrolimus 1%, which primarily targets T cells, led to almost complete clinical and histological remission of the skin lesions. Our report indicates that the therapeutically induced disappearance of the plasma cells was due to indirect T-cell-mediated effects.