Statin-induced autoimmune myositis: a proposal of an “experience-based” diagnostic algorithm from the analysis of 69 patients

Abstract

Statin-induced autoimmune myositis (SIAM) represents a rare clinical entity that can be triggered by prolonged statin treatment. Its pathogenetic substrate consists of an autoimmune-mediated mechanism, evidenced by the detection of antibodies directed against the 3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR Ab), the target enzyme of statin therapies. To facilitate the diagnosis of nuanced SIAM clinical cases, the present study proposes an “experience-based” diagnostic algorithm for SIAM. We have analyzed the clinical data of 69 patients diagnosed with SIAM. Sixty-seven patients have been collected from the 55 available and complete case records regarding SIAM in the literature; the other 2 patients represent our direct clinical experience and their case records have been detailed. From the analysis of the clinical features of 69 patients, we have constructed the diagnostic algorithm, which starts from the recognition of suggestive symptoms of SIAM. Further steps provide for CK values dosage, musculoskeletal MR, EMG/ENG of upper-lower limbs and, Anti-HMGCR Ab testing and, where possible, the muscle biopsy. A global evaluation of the collected clinical features may suggest a more severe disease in female patients. Atorvastatin proved to be the most used hypolipidemic therapy.

An atorvastatin‐induced positive anti‐HMGCR immune‐mediated necrotizing myopathy case

“…Only a few reported statin‐induced IMNM patients with positive anti‐HMGCR antibodies spontaneously resolved 2 . The most common therapy is prednisolone combined with another immunosuppressive agent such as methotrexate, azathioprine, or mycophenolate mofetil 6,8,9 . IVIg or rituximab can be added to support the treatment but preferentially IVIG 3,10,11 Triple therapy given in this case, which comprises IVIg, systemic corticosteroids, and a non‐steroidal immunosuppressant, has also been described in the literature 2,8 …”

“…There is no definite duration on how long after statin exposure a patient will develop IMNM—it can range from months to years 5 . Compared to other statins, atorvastatin was more frequently reported to be a cause of statin‐induced IMNM, likely due to its high lipophilic property resulting in better penetration to peripheral and liver tissues 6 …”

“… 5 Compared to other statins, atorvastatin was more frequently reported to be a cause of statin‐induced IMNM, likely due to its high lipophilic property resulting in better penetration to peripheral and liver tissues. 6 …”

An Atorvastatin-induced positive anti-HMGCR immune-mediated necrotizing myopathy case

“…In our case, the patient developed weakness a few months after statin initiation and continued to deteriorate even after statin discontinuation. Compared to other statins, atorvastatin was more frequently reported to be a cause of statin-induced IMNM, likely due to its high lipophilic property resulting in better penetration to peripheral and liver tissues 9 . Symptoms are milder at onset 50-60 years old while younger patients appear to be more severe and, regardless of statin use, are more recalcitrant to treatment.…”

“…IVIg or rituximab can be added to support the treatment but preferentially IVIG 3,11,12 Our case, the patient received triple therapy which comprises IVIg, systemic corticosteroids, and a non-steroidal immunosuppressant, which has been described as in the literature 2,5 . Symptom resolution time was approximately twelve months and might take longer in females at 16 months 9 . Most of the patients responded well to immunosuppressive treatment.…”