Methotrexate nodulosis.

Methotrexate (MTX) nodulosis in patients with rheumatoid arthritis treated with MTX has become a well recognized phenomenon. It has not been described in patients receiving MTX for treatment of other diseases, e.g., dermatological or malignant diseases. Recently, MTX nodulosis was described in a patient with psoriasis and arthritis. The pathophysiology and treatment of MTX nodulosis are yet unsettled. We experienced a case with dermatomyositis who developed multiple subcutaneous nodules after treatment with MTX. In our patient, numerous, small, symmetrically distributed, grouped subcutaneous nodules were seen on a V-shaped area of the anterior chest, both axillary areas, and the medial sides of both upper arms and thighs. We histopathologically examined a nodule and started treatment with hydroxychloroquine after discontinuation of MTX. The histopathology revealed septal panniculitis, and the nodules have been under regression. MTX nodulosis may be a drug-specific phenomenon. Discontinuation of MTX and replacement with hydroxychloroquine are recommended in severe cases. Awareness of this entity is important for diagnosing and treating cases of multiple nodules developing after the administration of MTX, which is widely used for many dermatological diseases.