Anti-HMGCR antibodies in systemic sclerosis

The prevalence and clinical characteristics of anti-HMGCR (anti-3-hydroxy-3-methyl-glutaryl-coenzyme A reductase) antibodies in idiopathic inflammatory myopathy: an analysis from the MyoCite registry

This study aimed to determine the prevalence and clinical characteristics of anti-HMGCR antibodies in idiopathic inflammatory myositis (IIM) at a tertiary care centre in northern India. Data (adult and children) were retrieved from the MyoCite dataset, identifying patients with polymyositis, dermatomyositis, and antibody-negative IIM whilst fulfilling the ACR/EULAR criteria. SLE, sarcoidosis, and systemic sclerosis were included for comparison as disease controls. The baseline clinical profile, laboratory tests, and muscle biopsies were retrieved and analysed. Descriptive statistics and non-parametric statistics were used for comparison. Among 128 IIM (112 adults, 16 children, M:F 1:2.8) of age 37 (24-47) years and 6 (3-17) months disease duration, 4 (3.6%) young adults tested positive for anti-HMGCR antibodies. All children and disease control tested negative for the antibody. Anti-HMGCR + IIM exhibited higher muscle enzymes [AST (367 vs 104 IU/L, p = 0.045), ALT (502 vs 78 IU/L, p = 0.004), and CPK (12,242 vs 699 IU/L, p = 0.001] except lactate dehydrogenase with less frequent systemic features such as fatigue than antibody-negative IIM. One young girl presented with a Limb-girdle muscular dystrophy (LGMD) with chronic pattern. None of the patients exhibited rashes, statin exposure, or cancer, though one had anti-Ro52 and mild disease. Our observations depict a younger population while affirming previous literature, including NM-like presentation, and chronic LGMD-like pattern of weakness in one case. Although a small number of children were included, ours is one of the few paediatric studies that evaluated HMGCR antibodies thus far. Further investigations in a larger Indian cohort are warranted to substantiate our findings.

Statin-associated anti-HMGCR immune-mediated necrotizing myopathy with dermatomyositis-like features: A case report

Anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) immune-mediated necrotizing myopathy is a subtype of idiopathic inflammatory myopathy which may be associated with statin exposure. It presents with severe proximal muscle weakness, high creatine kinase levels and muscle fiber necrosis. Treatment with intravenous immunoglobulins and immunosuppressants is often necessary. This entity is not commonly known among dermatologists as there are usually no extramuscular manifestations. We report a rare case of statin-associated anti-HMGCR immune-mediated necrotizing myopathy with dermatomyositis-like cutaneous features. The possibility of anti-HMGCR immune-mediated necrotizing myopathy should be considered in patients with cutaneous dermatomyositis-like features associated with severe proximal muscle weakness, highly elevated creatine kinase levels and possible statin exposure. This indicates the importance of muscle biopsy and specific autoantibody testing for accurate diagnosis, as well as significant therapeutic implications.

Anti-HMGCR Myopathy

Anti-HMGCR myopathy was first recognized and characterized in patients with a history of statin exposure and immune-mediated necrotizing myopathy. After the discovery of anti-HMGCR autoantibodies, several international groups identified and characterized more patients, expanding the phenotypic spectrum of this disease to include pediatric patients and young adults without statin exposure and those with a chronic myopathy resembling limb-girdle muscular dystrophy. We provide a summary of clinical findings, pathologic features, muscle imaging, and immunogenetic risk factors of the disease. We also discuss the current treatment strategies and approaches to monitoring the therapeutic response. Lastly, we briefly summarize the current understanding of the pathophysiology of the disease and postulate a model for autoimmunity initiation and propagation in this disease.