Late-onset dyshormonogenic goitrous hypothyroidism due to a homozygous mutation of the SLC26A7 gene: a case report

Abstract

Background: In this study, we used targeted next-generation sequencing (NGS) to investigate the genetic basis of congenital hypothyroidism (CH) in a 19-year-old Tunisian man who presented with severe hypothyroidism and goiter.

Case presentation: The propositus reported the appearance of goiter when he was 18. Importantly, he did not show signs of mental retardation, and his growth was proportionate. A partial organification defect was detected through the perchlorate-induced iodide discharge test. NGS identified a novel homozygous mutation in exon 18 of the SLC26A7 gene (P628Qfs*11), which encodes for a new iodide transporter. This variant is predicted to result in a truncated protein. Notably, the patient's euthyroid brother was heterozygous for the same mutation. No renal acid-base abnormalities were found and the administration of 1 mg of iodine failed to correct hypothyroidism.

Conclusions: We described the first case of goitrous CH due to a homozygous mutation of the SLC26A7 gene diagnosed during late adolescence.

Keywords: SLC26A7 gene; Case report; Congenital hypothyroidism; Dyshormonogenic goiter; Genetic analysis.

Fig. 1

Thyroid scintigraphy with 131I (a) and perchlorate discharge test (b)

Fig. 2

Sanger sequencing and segregation analysis of the pathogenic variant of the SLC26A7 gene. Patient’s sequence electropherogram showing the homozygous deletion of the C (a), brother’s sequence electropherogram showing the heterozygous deletion of the C (b) and family pedigree (c). Empty symbols with a “?” inside represent family members not investigated