CUTANEOUS PSEUDOLYMPHOMA DEVELOPING DURIN G LOW-DOSE METHOTREXATE THERAPY FOR RHEUMATOID-ARTHRITIS

Introduction. Over the last three years, there have been over twenty c ase reports of lymphoma in patients given low-dose methotrexate for rh eumatoid arthritis. We observed the first case of cutaneous pseudolymp homa. Case report. A 56-year-old man had been treated with methotrexat e (15 mg/day) for 6 years due to rheumatoid arthritis. He developed th ree isolated papulonodular ulcerations on the limbs. The histology and immunohistochemical examinations demonstrated T and B lymphoplasmocyt e infiltration without epidermotropism nor destruction of the annexes. Immunolabelling for anti-Epstein-Barr virus was negative. There was a IgG lambda type monoclonal hypergammaglobulinaemia, Bence-Jones prote inuria and an increase in beta 2-microglobulin. The thoracoabdominal s can, bone marrow biopsy and gallium scintigraphy were normal. There wa s no sign of a Gougerot-Sjogren syndrome nor of a Felty syndrome. The skin lesions and the Bence-Jones proteinuria disappeared rapidly after withdrawal of methotrexate. There has been no recurrence with a follo w-up of 16 months. Discussion. The diagnosis of pseudolymphoma was ret ained on the basis of the clinical features, the histological and immu nohistochemical evidence and especially on the clinical course after m ethotrexate withdrawal, i.e. spontaneous regression of the lesions wit hin 3 weeks. A similar course has been observed in three cases of lymp hocyte proliferation suggesting that this immunosuppressor would be th e most probable causative agent. Lymphocyte proliferation, mainly B-ce ll lymphomas in haematopoietic organs occurring under methotrexate adm inistration have occured mainly in patients with rheumatoid arthritis. Three cases have also been described in patients with dermatomyositis , but none have been reported in patients with psoriasis. This would s uggest that cofactors involved in these autoimmune diseases could also have an effect: immunodepression, potentialization due to associated treatment (corticosteroids), Epstein-Barr virus... Conclusion. Data on these observations should be combined in order to analyse the questio n of the safety of low-dose methotrexate in these patients.