Hearing loss with two pathogenic SLC26A4 variants and positive thyroid autoantibody: A case report.

SLC26A4 causes Pendred syndrome (PS) and nonsyndromic hearing loss. PS is distinguished based on perchlorate discharge test abnormality, goiter, and hypothyroidism in some patients. The pathophysiology of thyroid dysfunction in PS differs from that of autoimmune thyroid disease, in that it is considered to be caused by an iodide organification defect. It is believed that both diseases may incidentally coexist, and that SLC26A4 may play an important role in the etiology of autoimmune thyroid disease. Herein, we describe a case of a girl with hearing loss who had two pathogenic SLC26A4 variants and tested positive for thyroid peroxidase (TPO) antibody. She was diagnosed with hearing loss and vestibular aqueduct enlargement at the age of 4 yr. Deafness gene screening revealed two pathogenic SLC26A4 variants. As SLC26A4 variants can cause PS, the patient underwent thorough thyroid examination. Her thyroid gland was within the physiological range of mild enlargement. Although thyroid function test results were normal, the patient tested positive for TPO antibody. The patient was diagnosed with "suspected PS" and "suspected Hashimoto's thyroiditis," both of which increase the risk of developing hypothyroidism. Evaluating the comorbidity of Hashimoto's thyroiditis with the SLC26A4 variant in terms of complications is critical.