Abstract
Necrotizing autoimmune myopathy (NAM) is a group of severe acquired myopathies, characterized by prominent myofiber necrosis with little or no muscle inflammation. They can be misdiagnosed as muscular dystrophies, preventing initiation of appropriate therapy. Specific auto-antibody anti-Signal recognition protein is observed in 16% of cases. Recently, auto-antibodies against 3-hydroxy-3-methylglutaryl-coenzymeA reductase (HMGCR) were identified in NAM patients by one group, especially in statin exposed patients. Here we report the first European series of patients. We detected and quantified anti-HMGCR auto-antibodies using addressable laser bead immunoassay that we developed. Patients (n = 38) were 44 ± 19 years old (3 pediatric cases) and sex ratio male: female was 0.22. Statin exposure was recorded in 40% of patients. Patients suffered from myalgia (44%), and had a muscular deficit (92%). Subacute onset (less than 6 months) was noted for most of them (n = 18), nevertheless 10 patients had a slow progressive muscular deficit (10 months to years). Severe proximal weakness was observed (72%) and three patients were bedridden at the diagnosis. All patients had increase CK level (6630 ± 5990 UI/L). CK level correlated with muscular strength (r2 = −0.64, p = 0.005) and to anti-HMGR titer (r2 = −0.5, p = 0.04). None patients presented signs of pulmonary involvement. Mean duration of treatments (steroids, immunosupressant and/or IgIV) was 30.1 ± 36.1 [3–42] months, and to date it was not possible to stop the treatment for any patient. This the first study confirming the observation and the description of anti-HMGCR NAM. The majority of patients we detected was statin-naive, had a severe weakness and need prolonged treatments. Anti-HMGCR auto-antibodies testing may be warranted in dystrophic like patients. Anti-HMGR titer correlates with CK level suggesting their role in physiopathogenesis.
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