Clinical, myopathological and imaging features of pediatric anti-3-hydroxy-3-methylglutaryl- coenzyme A reductase myopathy / 中华神经科杂志

ABSTRACT

Objective:To determine the clinical, pathological and imaging phenotypes of pediatric patients with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) myopathy to explore its diagnostic strategies.Methods:The clinical features of 10 pediatric patients with anti-HMGCR myopathy in the Department of Neurology, Peking University First Hospital from July 2014 to July 2021 were collected. Muscle biopsies were performed in all patients, with histological, enzymatic histochemical and immunohistochemical staining.Results:The male to female ratio was 6∶4, the age of onset was 3-16 (8.3±3.7) years, 2 cases had subacute onset, and 8 cases experienced chronic progressive onset. All patients presented with neck and proximal muscular weakness of all limbs. Skin rash was observed in 2 cases. Serum creatine kinase was 998-27 981 U/L. The electromyography results were available from 6 cases, who experienced myogenic changes. The muscle magnetic resonance imaging was performed in 5 cases and revealed muscle edema predominantly in posterior compartment of thigh, with mild fatty infiltrate in 2 cases. An initial diagnosis was limb-girdle muscular dystrophy in 7 cases, but with subsequently negative genetic testing. Muscle biopsies revealed scattered necrotic fibers and regenerating fibers, complement deposition in sarcolemma basement-membrane areas of non-necrotic fibers and a few of lymphocyte infiltrate in all specimens. Moreover, a high frequency of major histocompatibility complex Ⅰ expression in muscle fibers was observed in 9 cases, proliferation of connective tissue of endomysium in 8 cases, muscle fiber hypertrophy in 4 cases and vacuoles in 2 cases.Conclusions:Pediatric anti-HMGCR myopathy is frequently misdiagnosed as muscular dystrophy. Systematic consideration of anti-HMGCR myopathy and testing for myositis specific antibody in children with genetically unconfirmed muscular dystrophy may help the differential diagnosis.