Successful treatment of a patient with lymphomatoid papulosis by methotrexate.

We report a case of lymphomatoid papulosis (LyP) that occurred in a 44-year-old Japanese male patient. Reddish papules with a small number of pustules and nodules were observed on the extremities, chest and upper back. Most lesions were also associated with central necrosis, ulceration and crusting, and regressed spontaneously within 4 to 6 weeks. Histopathological examination revealed wedge-shaped dense cellular infiltrate in the dermis, which was mixed with large atypical lymphoid cells, small lymphocytes, eosinophils and neutrophils. These large atypical cells expressed CD30 on their cell membrane and cytoplasm. Rearrangement of the T-cell receptor (TcR) beta-chain gene was detected in the skin lesion. Lymphadenopathy with histopathologic change similar to the skin lesions, but without TcR gene rearrangement, was found at the left inguinal area. Systemic administration of methotrexate (7.5-15.0 mg/week) was found to be dramatically effective in resolution of skin lesions and prevention of their recurrence.