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Abstract Details

A Case of Smoldering Anti-HMGCR antibody Myopathy
Neuromuscular and Clinical Neurophysiology (EMG)
P9 - Poster Session 9 (5:30 PM-6:30 PM)
Adult onset anti-HMGCR necrotizing myopathy is classically described as having a subacute but fulminant onset involving CK elevations in the 1-20,000 IU/L range with progressive proximal weakness following statin exposure despite statin cessation. Additional phenotypes have been described presenting as chronic limb girdle muscular dystrophy or in pediatric populations without statin exposure.

69 year-old woman with a history of diabetes, hyperlipidemia on atorvastatin for three years, morbid obesity, and congestive heart failure, presented with several months of pain and cramping in both calves. She denied associated back pain, numbness, tingling, or weakness. Neurologic exam showed isolated inability to toe-walk, limited by pain. She had normal strength, sensation, and reflexes. CK at the time of symptom onset was 510 U/L (<170 U/L). Atorvastatin was stopped and symptoms improved but did not resolve. One week and one month after atorvastatin cessation, CK was 809 and 604 U/L and aldolase was 17 and 8.1 U/L (<7.7 U/L), respectively. HMGCR Ab returned positive at 4000 (<2500). Due to her mild and improving symptoms, we planned to monitor without immunotherapy. She was lost to follow up.

She returned one year later with severe proximal weakness requiring a wheelchair and CK of 10,074 U/L. Repeat HMGCR Ab was 545.4 (<20.0 CU). EMG was consistent with irritative proximal myopathy. Muscle biopsy was consistent with necrotizing myopathy. She was started on prednisone 60mg daily, IVIG 2g/kg every 2 weeks and Cellcept 1000mg twice daily with improvement. Two years later, she can stand and transfer independently but remains primarily wheelchair bound.

This case highlights the potential for HMGCR myopathy to present with a period of calf pain and mild CK elevation (<1000 U/L). In patients with a smoldering onset, there may be a treatment window to prevent transformation into a more disabling classical phenotype.
Kathie Lin, MD (Stanford Neuromuscular Department)
Dr. Lin has nothing to disclose.