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Successful treatment of multicentric reticulohistiocytosis with leflunomide

SIR, We describe a patient with multicentric reticulohistiocytosis (MRH) who failed to respond to a combination of methotrexate, prednisolone, hydroxychloroquine, sulfasalazine and alendronic acid. Improvement in his condition followed shortly after the introduction of leflunomide. To our knowledge, this is the first report in the literature of the successful use of leflunomide to treat MRH. A 74-year-old man presented with a 2-month history of swollen fingers with nontender periungual papules and nodules arising along the edge of his fingers (Fig. 1a,b). One month later he developed arthralgia and a nonpruritic, photodistributed, erythematous rash on his anterior chest and shoulders. He also developed further nodules on his elbows (Fig. 1c) and inside his mouth. Past medical history included hypertension, hypercholesterolaemia, atrial fibrillation and high-grade follicular non-Hodgkin lymphoma, successfully treated with radical radiotherapy 11 years previously. Incisional biopsies were taken from papular and macular areas of the eruption, as well as from the buccal mucosa. All samples showed a dermal infiltrate consisting of sheets of histiocyte-like cells with abundant ‘glassy’ bright pink cytoplasm. There were occasional multinucleate cells; special stains showed diffuse CD68 positivity but negative AE1 ⁄AE2, S100 and CD34. There was some positive CD31 staining in a cytoplasmic membrane pattern. These findings were consistent with a diagnosis of MRH (Fig. 2). To rule out recurrent lymphoma, the patient underwent lymph node biopsy: this showed follicular reactive hyperplasia. Gastroscopy to exclude gastric lymphoma revealed abnormal folds at the pylorus; biopsy from this area showed histological changes consistent with MRH. Further malignancy screen included a normal computed tomographic scan of the chest, abdomen and pelvis. Tumour markers were normal (lactate dehydrogenase, prostate-specific antigen, Ca 19-9, carcinoembryonic antigen and CA125). Autoimmune profile