Abstract #1405039: Melting Muscle: Rhabdomyolysis as a Rare Initial Presentation of Hashimoto’s Thyroiditis

Abstract

Rhabdomyolysis is characterized by muscular necrosis and the release of intracellular muscle contents into circulation. The most common cause of primary hypothyroidism is Hashimoto’s thyroiditis (HT) in iodine-adequate areas. Although hypothyroid myopathy is commonly seen, rhabdomyolysis is a rare reported but serious complication in patients with HT. This case report aims to highlight this rare complication, so that diagnosticians will consider this in their differential diagnosis. A 44-year-old African American male with a history of asthma and hypertension presented to the emergency room due to mild generalized muscle cramps started several weeks ago. It worsened recently after he started a new job that required him to work in the yard for 3-6 hours daily. He denied any new medications, recent trauma, drug use, insect bites, sick contacts, recent travel, or strenuous exercise. His vital signs were stable. Initial laboratory workups were significant for elevated creatinine kinase at 4299 unit/L and creatinine of 1.57 mg/dl. Notably, his thyroid stimulating hormone was 42.94 uIU/mL, free thyroxine (T4) was 0.48 ng/mL, and his anti-microsomal antibody was >1300 units/mL. He was admitted to hospital for rhabdomyolysis secondary to Hashimoto’s thyroiditis. Levothyroxine therapy and intravenous fluid were given. His condition improved and was ultimately discharged with close primary and endocrinology follow-up. Hypothyroidism is well-associated with musculoskeletal problems, and it is estimated that around one-third of patients are accompanied with myopathy symptoms. Mechanism of hypothyroidism-induced myopathy is not fully understood. It is thought, however, to be linked to thyroxine’s role in glycogenolysis and mitochondrial oxidative processes. Thus, insufficiency of thyroxine may damage myocytes due to oxidative stress and may eventually lead to rhabdomyolysis. Although Hashimoto’s thyroiditis is recognized as one of the most common causes of hypothyroidism, as per our knowledge, this is the first case that a patient initially presenting with rhabdomyolysis was found out to have Hashimoto’s thyroiditis. Thus, hypothyroidism should be kept on the differential in patients with suspicion of rhabdomyolysis, and a thyroid panel should be considered as one of the initial workups.