Macrophagic myofasciitis: description and hypotheses

Purpose. - A new type of inflammatory myopathy of unknown etiology has rece ntly been described in France. The myopathy, called macrophagic myofasciiti s, had never been described in the literature. Methods. - In December 1998, 35 cases of macrophagic myofasciitis were repo rted, showing an increase in its incidence since the description of the fir st case in 1993. The first 22 cases are described. Results. - The 22 patients were each referred with a presumptive diagnosis of either polymyositis (11 patients), polymyalgia rheumatica (5 patients), mitochondrial cytopathy (4 patients), or congenital myopathy or muscle dyst rophy (1 patient for each). Clinical symptoms included myalgias (91%), arth ralgias (68%), marked asthenia (55%), muscle weakness (45%), and fever (32% ). Laboratory findings included elevated CK levels (50%) and a marked incre ased in the erythrocyte sedimentation rate (37%). Electromyographic recordi ngs showed the existence of myopathy (35%). Muscle biopsy showed a unique p attern characterized by: (i) centripetal infiltration of the epimysium, per imysium and perifascicular endomysium by non epitheloid, cells of the monoc yte/macrophage lineage (CD68+, CD1a-, S100-) with both large cytoplasm and PAS-positive content; (ii) absence of necrosis, of both epitheloid and gian t cells, and of mitotic figures; (iii) occasional CD8+ T-cells; and, (iiii) minimal myocyte suffering. The disease symptoms were easily distinguishabl e from those of sarcoid myopathy and fasciitis-panniculitis syndromes. Infe ctious diseases known to be associated with reactive histiocytosis, includi ng Whipple's disease, Mycobacterium avium intracellulare infection and mala koplakia, could not be documented. Patients' condition improved under corti costeroid therapy, associated or not with non-specific antibiotic therapy. Conclusion. - A new inflammatory muscle disorder of unknown etiology, chara cterized by a distinctive pathological pattern of macrophagic myofasciitis, is emerging in France. Diagnosis is based on muscular biopsy. Numerous cli nical, epidemiological and etiopathologic studies initiated by the GERMMAD (Groupe d'etudes et de recherche sur les maladies musculaires acquises) are in progress. (C) 1999 Elsevier, Paris.