Eosinophilic Myositis/Perimyositis

Eosinophilic myositis/perimyositis (EM/P) is a diverse rare idiopathic inflammatory muscle disease, presenting with mass swelling, tenderness, pain and weakness, and associated with cutaneous lesions and peripheral and/or tissue eosinophilia [1]. EM is well described in the veterinary literature as it primarily affects the masticator muscles of dogs [2]; it has recently been discussed in the rheumatologic [3] and dermatologic literature [4, 5]. The spectrum of EM comprises a group of heterogeneous disorders affecting the muscles and their supporting connective tissue structures, with infiltration of mononuclear cells and/or eosinophils [5]. A clinical variant of EM have been termed “idiopathic eosinophilic myosi-tis” [6], “subacute perimyositis” [7], or “relapsing eosinophilic perimyositis” [5, 8].

Relapsing eosinophilic perimyositis (REP) is a rare disease which appears as a part of the spectrum of eosinophilic myositis [5] and presents with an inflammation within per-imysium and often epimysium without associated necrosis, in contrast with eosinophilic myositis, where a myonecrosis and inflammation of the endomysium appears. Only 12 patients with REP have been reported [3, 5, 8–10]. Trueb et al. (1995) described a 48-year-old Caucasian man with a 27-year history of relapsing febrile myopathy. The cutaneous manifestations included blotchy erythema overlying the swollen thigh muscles, Gottron's papules on the dorsa of the finger joints and erythematous papules on the palms. Laboratory findings showed peripheral blood eosinophilia > 1.5 × 10⁹/l and histopathological features of eosinophilic perimysial inflammation [5].