Abstract
Immune mediated necrotizing myopathy (IMNM) is an acquired inflammatory myopathy. One form of the disease is associated with serum anti-HMGCR autoantibodies and significant proportion of patients has a history of statin treatment.
The disease is rare with the incidence estimated around 2-3 cases/100000 statin treated individuals. In contrast to direct statin toxicity, anti-HMGCR associated IMNM is an induced autoimmune disease.
Patients suffer particularly from severe muscle weakness, which may be occasionally totally immobilising. Very high serum creatine kinase levels are usually detected.
HMGCR (3-hydroxy-3-methylglutarylcoenzyme A reductase) is a pharmacological target of statins and the fact that patients develop autoantibodies against the enzyme suggests a possible effect of statins in induction of HMGCR antigenicity. Muscle histopathology shows predominant muscle fibre necrosis usually without concomitant lymphocytic infiltrates.
Most of the patients require long-term treatment with glucocorticoids or immunosuppressive drugs. In resistant cases use of intravenous immunoglobulins may be necessary as the only effective approach to improve the disease.