Resistance to thyroid hormone with a mutation of the thyroid b receptor gene in an eight-month-old infant — a case report

Abstract

Introduction: Resistance to thyroid hormone (RTHb) is a rare syndrome of impaired tissue responsiveness to thyroid hormones (THs). The disorder has an autosomal dominant or recessive pattern of inheritance. Most of the reported mutations have been detected in the thyroid hormone receptor b gene (THRB). Case report: Authors present an eight-month-old infant with poor linear growth, decreased body weight, tachycardia, positive family history, and neonatal features suggestive of RTHb. Both our patient and his mother had elevated free thyroxine, free triiodothyronine, and non-suppressed thyrotropin (TSH) concentration. The fluorescent sequencing analysis showed a heterozygous mutation c.728G>A in TRb gene. This pathogenic variant is known to be associated with THR. Conclusions: The clinical presentation of RTHb is variable, ranging from isolated biochemical abnormalities to symptoms of thyrotoxicosis or hypothyroidism. The syndrome should be suspected in patients with increased serum TH level, accompanied by a normal or elevated TSH concentration. The affected patients require individualised management.