Background Anti-HMG-CoA reductase (HMGCR) myopathy is characterized by proximal muscle weakness, necrosis of muscle fibers on biopsy, elevated serum creatine kinase (CK) levels, and anti-HMGCR autoantibodies1. Although statins are associated with anti-HMGCR myopathy in patients over 50 years old, some patients have no history of statin exposure. In a previous longitudinal analysis including 17 patients with anti-HMGCR myopathy followed over a mean of 26 months, we found that only statin-exposed subjects had improvements in strength and CK with treatment during the observed time period2.
Objectives Here, we studied factors influencing disease progression in an expanded cohort of anti-HMGCR patients treated with immunosuppressive therapy.
Methods A retrospective cohort study was conducted with all anti-HMGCR positive patients enrolled in the Johns Hopkins Myositis Cohort between May 2002 and June 2015. Anti-HMGCR antibodies were screened for by ELISA and verified by immunoprecipitating in vitro-transcribed and translated HMGCR protein. Anti-HMGCR levels, CK levels, and proximal muscle strength (on a 0–10 scale) were assessed. A multilevel linear regression model was used to identify clinical factors that influence recovery of strength over time.
Results We identified 104 anti-HMGCR positive patients, 77 (74%) of whom were exposed to statins. The clinical characteristics for each of three age groups divided into tertiles (<51, 51–61 and >61 years old) were similar except statin exposure, which was 97% for the older group compared to 37% for the younger group of patients. There was no statistical significant difference of the CK, anti-HMGCR antibody titers and muscle strength between the different groups.
We analyzed factors that might influence recovery of muscle strength in 81 patients with more than one visit (mean follow-up time of 2.7 years; SD 2.6, 0–12 years). Older age at onset and greater weakness at first clinic visit were associated with faster recovery times in univariate and multivariate analyses, whereas statin exposure had no statistically significant effect.
We identified a subgroup of young, African American, statin naive women who were refractory to treatment, compared to older patients of both races.
Conclusions The current study suggests that older age, rather than statin exposure, predicts faster recovery after initiating immunosuppressive treatment for anti-HMGCR myopathy. Four years after disease onset, ∼50% of patients older than 61, but only ∼25% less than age 51, had recovered full strength. We also found that a subset of young, African American women were refractory to treatment. Some of these had progressive weakness despite aggressive immunosuppressive therapy.
Mammen A, et al., Arthritis and Rheumatology, 2011
Werner J, et al., Arthritis and Rheumatology, 2012
Disclosure of Interest None declared