Abstract
Rhabdomyolysis is a pathological condition presenting with symptoms of localized or generalized myalgia and weakness, associated with an increase in serum creatine kinase level and, often leading to myoglobinuria and acute kidney injury. It has a wide range of etiologies. Immune-mediated necrotizing myopathy (IMNM) is a rare type of inflammatory myopathy, that leads to rhabdomyolysis, and it is divided into three different subtypes: anti-3-hydroxy-3-methylglutaryl-coA reductase (anti-HMGCR, anti-signal recognition particle (anti-SRP), and seronegative. There are slight differences in incidence, age of onset, clinical course, and prognosis between these subtypes. We describe the case of a 67-year-old female with myalgias and weakness of the thighs for six weeks. Laboratory findings showed marked rhabdomyolysis and severe acute kidney injury. The workup led to the diagnosis of seronegative immune-mediated necrotizing myopathy (IMNM) and treatment with corticosteroid and methotrexate was introduced, which led to marked clinical improvement.