What is the incidence of statin-induced dermatomyositis worldwide?

Statin-Induced Dermatomyositis: Worldwide Incidence

Statin-induced dermatomyositis is extremely rare worldwide, with only approximately 9 documented cases reported in the medical literature as of 2020. 1

Epidemiology of Statin-Related Muscle Effects

• Statin therapy carries a small but definite risk of myopathy when used alone, with severe myopathy reported in approximately 0.08% of patients taking lovastatin and simvastatin 2
• Elevations of creatine kinase (CK) greater than 10 times the upper limit of normal have been reported in 0.09% of persons treated with pravastatin 2
• Common non-specific muscle aches or joint pains occur in approximately 5% of patients on statins, similar to placebo rates in clinical trials, suggesting many may not be drug-related 2
• Statin-associated muscle symptoms (SAMS) occur in 1-5% of patients in randomized controlled trials but are more frequent (5-10%) in observational studies and clinical settings 2

Statin-Induced Inflammatory Myopathies

• Inflammatory myopathies associated with statins, including dermatomyositis, are characterized by persistence of symptoms even after discontinuation of the drug 3
• These conditions are distinct from self-limited myopathies and often require immunosuppressive therapy 3

Documented Cases of Statin-Induced Dermatomyositis

• The first case of fluvastatin-induced dermatomyositis was reported in a 76-year-old male patient who developed symptoms two months after starting the medication 4
• A case of pravastatin-induced dermatomyositis was reported in a 69-year-old patient who developed symptoms 2 years after starting treatment 5
• The first case of simvastatin-induced dermatomyositis was reported in a 71-year-old woman with positive Mi-2-Antibodies 6
• As of 2020, a comprehensive literature review identified only approximately 9 cases of statin-induced dermatomyositis reported worldwide 1

Risk Factors for Statin-Induced Muscle Effects

• Myositis is most likely to occur in persons with complex medical problems and/or who are taking multiple medications 2
• Risk factors include advanced age (especially >80 years), female sex, small body frame, multisystem disease (especially chronic renal insufficiency), and polypharmacy 7
• Drug interactions that affect statin metabolism, particularly those involving the cytochrome P-450 3A4 isozyme, increase risk 2
• Combinations with other medications including cyclosporine, fibrates, macrolide antibiotics, certain antifungal drugs, and niacin increase risk of myopathy 2

Clinical Course and Management

• Some cases of statin-induced dermatomyositis resolve spontaneously after withdrawal of the drug without requiring corticosteroid treatment 4, 5
• Other cases require immunosuppressive therapy, including high-dose corticosteroids, methotrexate, or intravenous immunoglobulin 5, 3
• One reported patient with statin-induced dermatomyositis died of respiratory failure (pulmonary fibrosis) despite treatment with oral cyclophosphamide 5

Clinical Implications

• Due to the widespread use of statins worldwide, dermatologists and clinicians should assess for history of dermatomyositis when prescribing statins 1
• Clinicians should inquire if patients with dermatomyositis-like presentations are taking or have taken statin medications 1
• Statin-associated autoimmune myopathy (with HMGCR antibodies) is a rare but serious condition that requires statin cessation and additional therapy directed at the autoimmune process 2