(Kiosk 6) A Case Report of Autoimmune Necrotizing Myopathy

Case Diagnosis: 17 year old previously healthy male presents with autoimmune necrotizing myopathy.

Case Description or Program Description: A 17-year-old previously healthy male presented to acute care with progressive symmetrical proximal weakness, fatigue, decreased appetite, difficulty walking and climbing stairs, and frequent falls. Laboratory workup showed creatine kinase 12,533, alanine transaminase 197, aspartate aminotransferase 291, erythrocyte sedimentation rate 22, C-reactive protein 2. He had elevated anti-signal recognition particle antibodies (SRP) of 90. Spine imaging showed no acute findings. Cerebral spinal fluid studies were negative. Electromyography of right upper and lower extremities showed prominent acute myopathic changes in proximal musculature consistent with proximal greater than distal myopathy without neuropathy, radiculopathy, or motor neuron disease. Muscle biopsy confirmed necrotizing myositis. He was treated with intravenous (IV) fluids for rhabdomyolysis and IV methylprednisolone for 3 days then 6 weeks of a steroid taper during which he had improvement in ability to move arms and legs. He was transferred to acute inpatient rehabilitation and completed his steroid taper. During acute rehabilitation, he had weekly IV steroid treatments, monthly rituximab, methotrexate and IV immunoglobulins (IG) infusions.

Setting: Acute inpatient and outpatient rehabilitation

Assessment/Results: His weakness improved and was able to walk in the pool. He continued to progress in the outpatient setting with aqua and land physical and occupational therapy, progressing from initial strength of 2/5 in bilateral shoulder abductors and 2-3/5 strength in bilateral hip flexors with distal extremities 4/5 throughout on admission to 4-5/5 strength in all extremities, ambulating 1200 ft independently during 6 minute walk test and completing a full flight of stairs independently 5 months after initial presentation.

Discussion (relevance): We present a case of autoimmune necrotizing myopathy demonstrating significant improvement with frequent steroid, rituximab, methotrexate and IVIG treatments and multidisciplinary therapies including aqua therapy.

Conclusions: This case demonstrates that autoimmune necrotizing myopathy responds well to IV steroid, rituximab, methotrexate and IVIG treatments combined with occupational and physical therapy.