Panniculite au cours d'un traitement d'une dermatomyosite par du méthotrexate

Panniculitis is a rare cutaneous manifestation of dermatomyositis (DM). The appearance of panniculitis during treatment with methotrexate (MTX) is exceptional and has only been described in 3 cases. We report a case of a 50-year-old woman suffering from DM since 1997 who was treated with corticosteroids showing favorable clinical and biological evolution. When a relapse occurred 2 years later, she was treated with higher-dose of corticosteroids in combination with a 7,5 mg weekly dose of methotrexate. The evolution was rapidly favorable. Eighteen months later, the patient had multiple subcutaneous nodules on limbs and buttocks. Anatomopathological examination showed panniculitis. There was no evidence supporting progression in DM. Prednisone dose was increased to 0.5 mg/kg/day, always in combination with MTX, without any clear signs of improvement. MTX treatment was stopped and the cutaneous lesions completely disappeared in 2 months without any relapse. This objective response lasted for 42 months. Our observation is particular given the occurrence of panniculitis in a patient undergoing treatment for dermatomyositis with methotrexate and illustrates the difficulties in the diagnosis. This entity must be known despite its exceptional nature since cutting off MTX treatment generally induces the disappearance of subcutaneous nodules.