Cancer association as a risk factor for anti-HMGCR antibody-positive myopathy.

Objective: To show cancerassociation is a risk factor other than statinexposure for anti- 3-hydroxy-3-methylglutaryl coenzymeA reductase autoantibody-positive (anti-HMGCR Ab+) myopathy. Methods: We analyzed the clinical features and courses of 33 patients (23 female and 10 male) with anti-HMGCR Ab+ myopathyamong 621 consecutive patients with idiopathic inflammatory myopathies. Results: Among the 33 patients, 7 (21%) were statin-exposed and 26 were statin-naive. In relation with cancer, there were 12 patients ( statin-exposed, n = 4) with cancersdetected within 3 years of myopathydiagnosis ( cancerassociation), 3 patients (all statin-naive) with cancersdetected more than 3 years before myopathydiagnosis ( cancerhistory), 10 cancer-free patients followed up for more than 3 years (all statin-naive), and 8 patients without cancerdetection but followed up for less than 3 years ( statin-exposed, n = 3). Therefore, 12 patients with cancerassociation (36%) formed a larger group than that of 7 statin-exposed patients (21%). Among 12 patients with cancerassociation, 92% had cancerdetection within 1 year of myopathydiagnosis (after 1.3 years in the remaining patient), 83% had advanced cancers, and 75% died of cancerswithin 2.7 years. Of interest, 1 patient with cancerhistory had sustained increase in creatine kinase level over 12 years from cancerremoval to the development of weakness. Conclusions: Patients with cancerassociation formed a large group with poor prognosis in our series of patients with anti-HMGCR Ab+ myopathy. The close synchronous occurrence of cancersand myopathiessuggested that cancerassociation is one of the risk factors for developing anti-HMGCR Ab+ myopathy.