A case of anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody-positive paraneoplastic necrotizing myopathy associated with advanced gastric cancer that responded to intravenous immunoglobulin therapy

Immune-Mediated Necrotizing Myopathy Manifesting after Five Years of Statin Therapy

Immune-mediated necrotizing myopathy (IMNM) is an increasingly common and serious condition in which autoantibodies attack muscle fibers causing clinically significant muscle weakness, fatigue, and myalgias. Recognizing the clinical presentation of IMNM is difficult but necessary, as rapid intervention decreases morbidity. We present a case of a 53-year-old female with IMNM induced by statin therapy with confirmed anti-3-hydroxy-3-methylglutaryl coenzyme A reductase antibodies present on serologic testing. The patient's statin therapy was halted, and the patient was provided with one dose of methylprednisolone and ongoing therapy with mycophenolate. She showed subsequent slow improvements in her muscle weakness and myalgias. It is important for clinicians to be aware of the possible consequences of statin therapy, as these drugs are generally regarded as benign in the medical community. Clinicians should also be aware that statin-induced myopathy can occur at any time during statin therapy. The condition does not necessarily correlate with beginning a new statin medication, as demonstrated in this case in which the patient was on chronic statin therapy before developing symptoms. Continued clinician education and building the fund of medical knowledge regarding this disease are vital to enable clinicians to recognize this disease and act promptly to reduce patient morbidity and improve outcomes.

Resection of Gastric Cancer Remitted Anti-signal Recognition Particle Myopathy

A 72-year-old woman presented with gradually-worsening myalgia and muscle weakness of the proximal lower limbs as well as elevated serum creatine kinase level. Based on a clinicoseropathological examination including a muscle biopsy, she was diagnosed with anti-signal recognition particle (SRP) myopathy. Although the myopathy relapsed two times in two years under oral prednisolone and intravenous immunoglobulin therapy, the myopathy remained in remission for more than three years after resection of gastric cancer. Although the anti-SRP myopathy is not considered to be cancer-associated in general, we should note that some cases of anti-SRP myopathy may be ameliorated with appropriate cancer treatment.

Clinical Problem Solving: An Older Woman With Weakness from Head to Toe

A 67-year-old woman was admitted to our hospital for progressive weakness, dysphagia, muscle pain, and weight loss. Here we detail the clinical problem solving involved in diagnosing and treating her immune-mediated necrotizing myopathy caused by anti-HMGCoA reductase autoantibodies. Interestingly, this diagnosis coincided with discovery of a gastrointestinal stromal tumor (GIST) and positivity for anti-nuclear matrix protein (anti-NXP2), another myositis specific autoantibody.

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.