Case Presentation: A 75-year-old Caucasian female with a history of hyperlipidemia treated with statin presented to the emergency room for generalized weakness. She became completely bedbound over the course of 5 days. Examination showed symmetric muscle weakness with power 2/5 at proximal muscles but normal strength in distal muscles. Deep tendon reflexes were decreased. She was unable to sit or stand without support. There was no sensory loss, muscle atrophy, fasciculation, skin rash or active arthritis. Laboratory studies showed significantly elevated creatine phosphokinase (CPK) of 5895 units/L and transaminases with AST of 1664 units/ L, ALT of 882 units/ L, alkaline phosphatase of 986 units/ L and total bilirubin of 7 mg/dL. TSH, ESR, and CRP were within normal range. Hepatitis panel, Acetaminophen & Salicylate levels were negative. She was initially treated for Statins induced myopathy by aggressive hydration and discontinuation of statin, however, CPK and LFTs trended up with CPK rising up to 23,250 units/L. Immunologic testing was positive for Anti-smooth muscle antibodies but negative for anti SSA/SSB, Anti-Jo1, Antimitochondrial (anti-MA) antibodies, Anti-ds DNA, P-ANCA and C-ANCA ruling out Sjogren’s syndrome, SLE, Idiopathic inflammatory myopathy, primary biliary cirrhosis or any another vasculitis. Muscle biopsy showed type 2 fiber atrophy and necrotizing myopathy without any inflammatory infiltrates. CT abdomen revealed evidence of cirrhosis with evidence of Ascites. The patient refused liver biopsy. The patient was started on high dose steroids with a good biochemical response. She was then transitioned to slow tapering of steroids over a course of 6 weeks and her condition improved significantly with gradual normalization of CPK in 2 weeks and LFTs in 6 weeks. She achieved her baseline functions status at around 4 weeks.
Discussion: Statins is among one of the most commonly used medications, associated with diverse muscle-related side effects including myalgia, myositis, overt rhabdomyolysis and necrotizing myopathy. Polymyositis(PM) is an autoimmune inflammatory muscle disorder characterized by the development of proximal and often symmetrical muscle weakness. PM can be rarely associated with Autoimmune hepatitis (AIH), which is a chronic progressive hepatitis of unknown origin, characterized by hepatitis, hypergammaglobulinemia, and autoantibodies. Both PM and Statin-induced myopathy may present with a diverse spectrum of muscle weakness and therefore diagnosis can be challenging. In our case, the biopsy showed only type 2 fiber atrophy and necrotizing myopathy without any inflammatory infiltrates. Statin-induced necrotizing myopathy fails to improve only with its discontinuation and requires immunosuppressive therapy. The absence of inflammatory cells can suggest lack of an autoimmune mechanism of myopathy in our patient. However, the presence of newly diagnosed AIH with the temporal association of muscle weakness favors PM associated with AIH, as the cause of myopathy in our patient. Besides, lack of inflammatory cells on biopsy does not always rule out polymyositis. Hence, the diagnosis remains a dilemma in our case.
Conclusions: Statins are a well-known cause of a wide spectrum of muscle diseases, most of which are self-limited and improve with its discontinuation. However, in absence of good biochemical or clinical response, other diagnoses should be suspected and appropriately managed.