(Kiosk 3) Immune-mediated Necrotizing Myopathy Mimicking Guillain-barre Syndrome Following COVID-19 Booster: A Case Report

Case Diagnosis: Necrotizing myopathy in the setting of COVID-19 booster.

Case Description or Program Description: A 71 year old male who received a COVID vaccine booster one month prior to admission presented with progressive lower extremity weakness complicated by multiple falls. Patient was found to have significant paraparesis with absent reflexes. Lumbar puncture revealed albumin-cytologic dissociation. He was also found to have elevated creatine kinase (CK) levels. Imaging of the neuraxis was unremarkable. The diagnosis of Guillain-Barre syndrome (GBS) and rhabdomyolysis were made. He was treated with steroids and a course of intravenous immune globulin (IVIG) for five days. However, there was no significant change in his weakness. CK levels continued to rise despite intravenous fluids.

Setting: Inpatient rehabilitation facility.

Assessment/Results: Myositis antibody panel resulted negative. Further investigation with deltoid muscle biopsy revealed necrotizing myopathy. Patient was started on a prolonged course of high dose steroids with improvement in CK levels and gradual improvement in weakness.

Discussion (relevance): Inflammatory myopathy (IM) belongs to a rare group of autoimmune inflammatory disorders characterized by muscular weakness and multi-system involvement. Immune-mediated necrotizing myopathy (IMNM) is one distinct subtype. Our patient presented with subacute to chronic proximal weakness with rhabdomyolysis not responding to intravenous fluids and a presumed GBS diagnosis unresponsive to IVIG. It is understood that vaccines exert a stimulatory effect on the immune system and have the potential to induce or exacerbate serologic findings or clinical autoimmune diseases.

Conclusions: This case report highlights the adverse events following a booster vaccine and abnormal serologic findings which prolonged patient’s recovery due to an incorrect diagnosis. Clinicians should be aware of vaccine-induced inflammatory myositis which may be confirmed by measuring muscle enzyme levels, myositis autoantibodies and performing muscle biopsy. Moreover, this case report highlights the importance that elevated CK levels with a negative myositis panel should not deter practitioners from further investigation with muscle biopsy.