NEUROMUSCULAR JUNCTION RELATED DISORDERS: EP.295 Brachio-cervical inflammatory myopathy associated with myasthenia gravis

Abstract

Among idiopathic inflammatory myopathies (IIM), brachio-cervical inflammatory myopathy (BCIM) constitutes a rare entity basically characterized by progressive weakness in the proximal regions of the arms and neck, the frequent association with other autoimmune diseases, and peculiar histopathological features at muscle biopsy. A 57-year-old woman presented with a 1-yr history of weight loss (-10kg), cervicalgia, bulbar signs and weakness in upper limbs. Clinical examination showed drop head with cervical muscle atrophy, severe proximal muscle weakness in upper limbs and nasal voice with swallowing disorders. No sign of scleroderma. Biological assessment disclosed increased CK serum levels and anti-AChR and anti-Scl autoantibodies. EMG showed myogenic changes in upper limbs but no decrement. Deltoid muscle biopsy revealed type-II fiber atrophy, randomly distributed active myonecrosis, and nodular inflammatory infiltrates, mainly perivascular. Immunohistochemical techniques showed ubiquitous myofiber expression of major histocompatibility complex (MHC)-class I and multifocal MHC-II-expressing myofibers. B-cells (CD20) were majority in infiltrates. C5b-9 immunostaining showed deposition in endomysium and capillaries walls. Significant clinical improvement was observed under medical treatment (anticholinesterase, corticosteroid, immunoglobulin and rituximab), ventilatory and nutritional support. Present case enlightened the specificities of BCIM, including (i) the remarkable distribution of muscle deficit, (ii) the frequent association with myasthenia gravis, and (iii) the highly recognizable histopathological pattern with active myopathy, C5b-9 staining of endomysium, focal perivascular and perimysial inflammation often with a prominent B cell component. Treatment is usually modeled on that of IIM, but considering histopathological features and the association with myasthenia, BCIM could constitute a privileged indication for anti-CD20 biotherapy.