Development of Hypothyroidism in a Patient with ATTRv Amyloidosis Following Patisiran Administration

Patisiran is a disease-modifying RNA interference agent for ATTRv amyloidosis caused by transthyretin gene mutations. We herein report a case of hypothyroidism in a 70-year-old man with ATTRv amyloidosis after treatment with patisiran. Although his neurological function score did not deteriorate, non-pitting edema and weight gain appeared approximately 13 months after treatment, and blood tests revealed hypothyroidism. The symptoms and thyroid function improved after treatment with levothyroxine. This is the only case of hypothyroidism among 317 patients reported in a nationwide post-marketing surveillance study of patisiran. In ATTRv amyloidosis, long-term changes in thyroid function should be monitored regardless of the response to patisiran.