Anti-HMGCR autoantibodies in self-limiting statin-induced myopathy

Statin-Associated Autoimmune Myopathy: Review of the Literature

OBJECTIVE

Statin-associated autoimmune myopathy (SAAM) is a rare adverse event characterized by progressive muscle symptoms despite discontinuation, requiring immunosuppressive therapy for remission. The objective of this review was to characterize SAAM, for timely detection, while examining the literature for effective treatment considerations.

METHODS

PubMed search was conducted from 2010 to 2020 was for relevant case series and studies of at least 8 patients displaying muscle discomfort or weakness, anti-HMGCR antibodies, exposure to statins, and biopsies consistent with SAAM.

RESULTS

Three case series and 3 case cohort studies identified 199 patients with SAAM. Exhibiting a mean age of 63.74 years, patients were more likely Caucasian (81%) and female (1.2X), and required a mean duration of 4.75 years before symptomatic. The presentation involved proximal muscle weakness (94%), myalgias (37%) and dysphagia (23%), accompanied by a mean creatinine kinase of 6383 IU/L. Most patients (57%) required 2 or more immunosuppressive (IMS) agents to achieve 62% remission. After 2 years of treatment, 15% of patients without remission reported symptomatic improvement, while another 12% were refractory to treatment.

CONCLUSION

Delayed onset of SAAM greater than 4 years from statin initiation may create a low index of suspicion. However, progression of symptoms beyond 2 months from statin discontinuation and positive anti-HMGCR antibodies requires immunosuppressive agents. Data and expert opinion support use of at least two IMS medications upon diagnosis for a minimum of 2 years. Therapy success depends on timely recognition and initiation of IMS combinations to achieve earlier remission and symptomatic improvement.

Treatment experience of Taiwanese patients with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase myopathy

Immune-mediated necrotizing myopathy (IMNM) has emerged as a new subgroup of idiopathic inflammatory myopathy in the past decade, associated with the presence of two autoantibodies against signal recognition particle and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR). We aim to analyze the clinical, pathological, and imaging phenotypes of the patients with anti-HMGCR myopathy in our cohort. Five patients with anti-HMGCR myopathy have been enrolled who were all female; three were pediatric and two were adult patients. The muscle pathology of patients met the diagnostic criteria of IMNM. On muscle magnetic resonance imaging, adductors were earliest affected while lower legs were relatively preserved with highest degree of involvement in medial head of gastrocnemius. In upper extremities, biceps brachii was the most severely involved, followed by triceps. All patients were refractory to steroid mono-therapy. For pediatric patients, all three patients eventually became responsive to steroid with either intravenous immunoglobulin or rituximab despite variable motor function recovered at present due to different intervention timing. For adult patients, one with statin exposure responded well to steroid and azathioprine use and the motor function returned to the baseline. The other adult patient finally got stabilized and slowly improved with steroid and methotrexate 13 years after the start of therapy. The creatine kinase (CK) levels of all patients were decreased along with clinical severity. In conclusion, muscle imaging might be of help for the diagnosis. Treatment with immuno-suppressants could be considered together with steroid from the beginning.

Statin-Associated Autoimmune Myopathy: Current Perspectives

Although generally well tolerated, statin users frequently report muscle-related side effects, ranging from self-limiting myalgias to rhabdomyolysis or the rare clinical entity of statin-associated immune-mediated necrotizing myopathy (IMNM). Statin-associated IMNM is based on the development of autoantibodies against 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in cholesterol synthesis and the pharmacologic target of statins, and leads to a necrotizing myopathy requiring immunosuppressive therapy. This review attempts to recapitulate the diverse aspects of anti-HMGCR IMNM, including clinical presentation, diagnostic modalities, genetic risk associations, therapeutic options and potential pathogenetic pathways.

An overview of statin-induced myopathy and perspectives for the future

Introduction: Statins remain the most commonly prescribed lipid-lowering drug class for the treatment of atherosclerotic cardiovascular disease. Their well-recognized side effects are known as statin-associated muscle symptom (SAMS). Some advances in this field have been made in recent years, but the understanding of the mechanisms has lagged. Investigating the specific role of the anti-HMGCR autoantibody, pharmacokinetic genetic variants, characterization of the known phenotypes of statin toxicity, in relation to clinical markers of disease, is of high importance.Areas covered: We summarized currently available findings (on PubMed) related to SAMS and discussed the therapeutic approaches, risk factors, drug interactions, potential novel systems, algorithms and biomarkers for SAMS detection. CoQ10 supplementation has been suggested as a complementary approach to manage SAMS, while vitamin D levels may be useful for both the diagnosis and management.Expert Opinion/Commentary: Further studies might help to understand the easiest way to diagnose SAMS, suitable prevention and an effective non-statin therapy. This review sheds new light on the future directions in both research and clinical practice, which will help with rapid risk assessment, identification of the SAMS risk factors in order to decrease the incidence of statins' adverse effects, and the most effective therapy.

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.

Bench to bedside review of myositis autoantibodies

Idiopathic inflammatory myopathies represent a heterogeneous group of autoimmune diseases with systemic involvement. Even though numerous specific autoantibodies have been recognized, they have not been included, with the only exception of anti-Jo-1, into the 2017 Classification Criteria, thus perpetuating a clinical-serologic gap. The lack of homogeneous grouping based on the antibody profile deeply impacts the diagnostic approach, therapeutic choices and prognostic stratification of these patients. This review is intended to highlight the comprehensive scenario regarding myositis-related autoantibodies, from the molecular characterization and biological significance to target antigens, from the detection tools, with a special focus on immunofluorescence patterns on HEp-2 cells, to their relative prevalence and ethnic diversity, from the clinical presentation to prognosis. If, on the one hand, a notable body of literature is present, on the other data are fragmented, retrospectively based and collected from small case series, so that they do not sufficiently support the decision-making process (i.e. therapeutic approach) into the clinics.