Frequent Seronegative Primary Hypothyroidism in Myxedema Coma in Japan: Three Case Reports With a Systematic Review.

Myxedema coma is a rare life-threatening form of hypothyroidism that manifests as neuropsychiatric, metabolic, respiratory, and cardiovascular dysfunction. From 2010 to 2022, our hospital managed three cases of myxedema coma. While the overall characteristics of these cases were similar to those in previous reports, we noticed that all cases were negative for thyroid autoantibodies and an autopsy in one of the cases exhibited end-stage thyroiditis. During a systematic review of cases from 1999 to 2022, we also noticed that a significant proportion of myxedema coma was caused by seronegative primary hypothyroidism especially in Japan.