Slowly Progressive Limb-Girdle Weakness and HyperCKemia – Limb Girdle Muscular Dystrophy or Anti-3-Hydroxy-3-Methylglutaryl-CoA-Reductase-Myopathy?

Background: Anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR)-myopathy is a usually rapidly progressive form of immune-mediated necrotizing myopathy (IMNM). Rarer clinical courses show slow progression and resemble the phenotype of limb-girdle dystrophy (LGMD). Objective: We demonstrate the difficulties in differentiating LGMD versus anti-HMGCR-myopathy. Methods: We report on a 48-year-old patient with slowly progressive tetraparesis and hyperCKemia for more than 20 years. Results: Due to myopathic changes in initial and second muscle biopsy and typical clinical presentation, the patient was diagnosed with LGMD 20 years ago; despite comprehensive genetic testing including exome diagnostics, the genetic cause of disease could not be identified. Finally, HMG-CoA reductase antibodies were detected, confirming the diagnosis of anti-HMGCR-myopathy. By re-work-up of a second muscle biopsy specimen from year 2009, the diagnosis of a IMNM was made in retrospect. Seven cycles of high-dose immunoglobulins were administered; patient reported outcome measures have mildly improved. Conclusion: Patients with clinical LGMD phenotype, degenerative changes in muscle biopsy but without genetic confirmation of the disease should be tested for HMG-CoA-myopathy, thereby allowing for an early start of treatment.