Screening for antibodies against the HMCGR antigen is performed in patients with possible immune-mediating necrotizing myopathy (IMNM). HMCGR antibodies are closely associated with prior statin therapy.
HMG-CoA reductase antibodies (HMGCR) are associated with autoimmune necrotizing myopathy and can be detected in 25% of these patients. Significantly elevated levels of creatine kinase (CPK) in the blood are often observed. Severe central muscular weakness is characteristic, whereas lung involvement is less frequent. Almost half of the patients have previous statin therapy. HMGCR antibody titer correlates with muscle strength and creatine kinase level in the blood. Myositis associated with HMGCR antibodies responds relatively well to immunosuppressive therapy. HMGCR antibodies are usually not detected in healthy individuals or in individuals with other inflammatory and autoimmune diseases. The concomitant presence of autoantibodies against SRP and HMGCR can occur occasionally and is unfavorable.
HMG-CoA reductase is an enzyme that catalyzes the reaction between HMG-CoA and mevalonate in the biosynthetic pathway of cholesterol. The discovery of HMG-CoA reductase inhibitors, known as statins, was a breakthrough in the treatment of hypercholesterolemia. Statins are used to prevent cholesterol biosynthesis.