Case Presentation: 70-year-old Caucasian lady with medical history of dyslipidemia, lumbar degenerative disease presented to the emergency department after being referred by her primary care physician (PCP) with a complaint of generalized weakness for about two years which worsened over the past six months. She initially had weakness in her lower limbs and had difficulty going up the stairs, progressed to her using raised toilet seat. Subsequently, it further progressed towards severe generalized weakness resulting in falls. Atorvastatin was stopped about six months before the presentation as a possible offending agent for weakness and pain in muscles. Her condition continued to worsen and hampered her daily activities; hence she was seen by neurology as outpatient. Magnetic resonance imaging of cervical spine and brain as outpatient showed mild central stenosis of cervical spine and no other abnormalities. Electromyography showed diffuse sensory and distal motor neuropathy, and elevated Creatine phosphokinase (CPK) of 2613. PCP started a ten-day course of prednisone, without improvement in her symptoms, hence referred to the Emergency department. Physical examination on presentation to our center showed weakness of neck flexors 4/5, deltoid 3/5, hip flexors 3/5 quadriceps 4/5 motor strength. Distal upper and lower extremity strength was 5/5. Exam was unremarkable for muscle atrophy, heliotrope rash, Gottron’s papules, shawl sign, nail fold erythema, or joint tenderness. Labs were remarkable for leukocytosis of 12 x10E+09/L and elevated CPK of 1592 U/L. Autoimmune work-up revealed elevated Aldolase 10.9 U/L (normal 0.0-8.1 U/L), Normal ANA; negative MI2, SM/RNP, Jo-1, SRP, CCP, ANCA antibodies. Normal TSH, ESR, CRP, RF, c3/c4 levels and negative hepatitis screen. Deltoid muscle biopsy showed necrotizing myopathy without lymphocytes. Barium swallow was normal, Imaging did not show any interstitial lung disease or any suspicion of malignancy. HMG-CoA reductase antibody came back positive with titer 135 U (normal< 20 units). Patient started on high-dose IV steroids along with IVIG. Steroids were slowly tapered over a month to 10 mg daily. She required monthly IVIG infusions for an initial 4 months, the frequency was reduced to once in three months, and completely stopped nine months after starting treatment. Her strength gradually improved to her normal self with the above treatment and physical therapy. She was not further challenged with statins for dyslipidemia.
Discussion: The common side effects of statins include rhabdomyolysis, hepatotoxicity, diabetes mellitus, and myopathy (1) with muscle-related side effects being more common (2). Normally, in statin myopathy the symptoms resolve after stopping the statin, however in Statin induced immune-mediated necrotizing myopathy (SIANM) the symptoms do not resolve even after discontinuing for several months and severe cases will need either glucocorticoids, IVIG or immunosuppressive therapy for symptom resolution (3). This type of myopathy should be differentiated from other types of necrotizing myopathy.
Conclusions: Persistence of proximal muscle weakness, myalgias, and elevated CK levels, two times or higher than the upper limit even after discontinuation of statins should be a stimulus to physicians to keep SINAM high among the differentials (4). Early cessation of statins and prompt therapy is associated with better remission rates and decreased morbidity and mortality (1).