A Pediatric Case of Granulomatous Myositis and Response to Treatment

Idiopathic inflammatory myopathy encompasses a group of acquired, heterogeneous, systemic diseases of the skeletal muscle, including adult polymyositis, adult dermatomyositis, juvenile dermatomyositis, juvenile polymyositis, inclusion body myositis, and necrotizing myopathy, all resulting in muscle weakness. Granulomatous myositis (GM) is a rare myopathy disorder histologically characterized by the development of endomyseal and/or perimyseal granulomas in striated muscle. GM is often associated with sarcoidosis. GM has also been associated with myasthenia gravis, inflammatory bowel disease, thymoma, and malignancy. We are reporting a rare case of a 13-year-old girl with GM without associated disease that was refractory to multiple medications, and responded well to rituximab.

Granulomatous Myositis Associated with Myasthenia Gravis: A Rare Case

Myasthenia gravis (MG) is an immune-mediated disease of the neuromuscular junction mediated by anti-acetylcholine receptor (AChR) antibodies (Ab). Granulomatous Myositis (GrM) is a histological diagnosis characterized by the presence of epithelioid granuloma in striated muscles. Few cases describing the presence of concomitant thymoma and non-thymoma-related MG with GrM have been reported. This present case is an addition to the literature describing the presence of concomitant thymoma and non-thymoma-related MG with GrM. The patient described is a 77-year-old male who started developing weakness and atrophy involving the musculature of the bilateral lower and upper extremities. Initial laboratory workup showed an elevated level of serum creatine phosphokinase (CPK) of 1,231 U/ L (reference range: 22 to 198 U/L). The right quadriceps muscle biopsy performed showed inflammatory infiltrates containing eosinophils, plasma cells, and lymphocytes forming multinucleate giant cells consistent with a diagnosis of GrM. Detailed laboratory and imaging work conducted to rule out an underlying cause of GrM showed elevated titers of AChR Ab (79.50 nmol/L, reference range: <0.02 nmol/L) and striational Ab (titer: 1:320, reference range < 1:120). A positive repetitive nerve stimulation test for the left ulnar nerve (decrement in the amplitude of muscle action potential by 13%) further confirmed the diagnosis of MG concomitant with GrM. Computed tomography of the chest was negative for the presence of a thymoma. The patient was started on treatment with oral prednisone and mycophenolate mofetil, which resulted in an improvement of symptoms and the downward trending of serum CPK level.

Extranodal NK/T-cell Lymphoma Mimicking Granulomatous Myositis

Extranodal NK/T-cell lymphoma (ENKTL) is an aggressive non-Hodgkin lymphoma that typically develops in the upper aerodigestive tract. We encountered an ENKTL patient who presented with generalized muscle weakness with eyelid swelling, diplopia, and facial edema. A muscle biopsy revealed lymphocytic infiltration without significant atypia; some lymphocytes formed granuloma-like structures. Although the initial response to steroids was encouraging, an ulcerative eruption appeared in the thigh, and a skin biopsy revealed lymphocytes with atypia. A re-analysis of the muscle biopsy with additional immunohistochemistry revealed neoplastic NK/T lymphocytes in the granulomatous structures. Our case highlights the significance of re-evaluating muscle biopsy specimens in cases of atypical myositis.

Respiratory muscle involvement in sarcoidosis

INTRODUCTION

In sarcoidosis, muscle involvement is common, but mostly asymptomatic. Currently, little is known about respiratory muscle and diaphragm involvement and function in patients with sarcoidosis. Reduced inspiratory muscle strength and/or a reduced diaphragm function may contribute to exertional dyspnea, fatigue and reduced health-related quality of life. Previous studies using volitional and non-volitional tests demonstrated a reduced inspiratory muscle strength in sarcoidosis compared to control subjects, and also showed that respiratory muscle function may even be significantly impaired in a subset of patients. Areas covered: This review examines the evidence on respiratory muscle involvement and its implications in sarcoidosis with emphasis on pathogenesis, diagnosis and treatment of respiratory muscle dysfunction. The presented evidence was identified by a literature search performed in PubMed and Medline for articles about respiratory and skeletal muscle function in sarcoidosis through to January 2018. Expert commentary: Respiratory muscle involvement in sarcoidosis is an underdiagnosed condition, which may have an important impact on dyspnea and health-related quality of life. Further studies are needed to understand the etiology, pathogenesis and extent of respiratory muscle involvement in sarcoidosis.