(735) Hashimoto Encephalopathy in a Previously Healthy Pediatric Child

Introduction: Hashimoto’s encephalopathy (HE) is an autoimmune thyroiditis encephalopathy and myxedema encephalopathy. It is characterized by acute encephalopathy, elevated antithyroid antibodies, and exclusion of infection, malignancy, toxicity, or other metabolic processes. The prevalence of pediatric Hashimoto thyroiditis (HT) is about 1.2%, occurring predominantly in females with a female-to-male preponderance of at least 4:1. HE is a rare diagnosis, with few literature reports, and is one that is often misdiagnosed early in its course.

Description: A previously healthy 14-year-old female was admitted for seizure-like activity followed by depressed mental status and encephalopathy. She was intubated for hypercarbia and airway protection. EEG revealed diffuse slowing without seizure activity. MRI of the brain was normal aside from a prominent pituitary gland. A comprehensive infectious work-up was performed, which was reassuring aside from a mild leukocytosis and elevated inflammatory markers. Labs revealed an elevated TSH, a depressed free T4, and positive anti-thyroid peroxidase antibodies with a negative anti-thyroglobulin antibody test. Given the abnormal thyroid hormone levels indicating a hypothyroid state along with increased TPO antibodies, a probable diagnosis of Hashimoto’s encephalopathy was made. The patient made a full recovery after treatment with levothyroxine, steroids, and anti-epileptics.

Discussion: The hallmark feature of HE is a nonspecific encephalopathy that involves an altered mental status and level of consciousness that may range from confusion and impaired cognitive function to coma. There is no correlation of HE occurring with specific thyroid hormone levels, adding to the complexity of its diagnosis. Seizure disorders have been reported to be the first manifestation in approximately 2/3 of HE patients; however, the seizures associated with HE respond poorly to anti-epileptic medications. HE is a rare complication of HT, and few pediatric cases have been reported. More than 20% of children have been found to have persistent neurological deficits after 4 years of follow-up. Prognosis is often poor in patients who have a delayed time to diagnosis, emphasizing the need to be considered within the differential and highlighted within the literature.