Statin-induced necrotizing autoimmune myopathy: an extremely rare adverse effect from statin use

Area of Science:

• Immunology
• Neurology
• Pharmacology

Background:

• Statins are commonly prescribed for cardiovascular event prevention.
• Statin-induced necrotizing autoimmune myopathy (SINAM) is a rare autoimmune condition.
• SINAM is distinct from more common, self-limited statin myopathy.

Observation:

• A 71-year-old male developed severe bilateral lower-extremity weakness after 10 years of atorvastatin use.
• Physical examination revealed muscle wasting and proximal muscle weakness.
• Laboratory tests showed elevated muscle enzymes, inflammatory markers, and high anti-HMGCR antibodies.

Findings:

• Muscle biopsy confirmed myositis with specific C5b-9 deposits.
• Diagnosis of SINAM was established based on clinical presentation, elevated anti-HMGCR antibodies, and biopsy results.
• Treatment involved statin discontinuation, steroids, immunoglobulins, and azathioprine, leading to gradual improvement.

Implications:

• SINAM is a severe myopathy characterized by significant weakness and elevated creatine kinase levels.
• Anti-HMGCR antibodies are a hallmark of SINAM, present in all cases.
• Physicians must be aware of SINAM, as immunosuppressive therapy is the primary treatment, and statin re-challenge is contraindicated.