[Partial thyroxine binding globulin deficiency in test tube infants: report of cases and literature review]

Abstract

Objective: To investigate the clinical characteristics of twins with thyroxine binding globulin (TBG) deficiency and to find SERPINA7 gene mutations.

Method: Data(2015) related to clinical characteristics, serum biochemistry, gene mutations and pedigree of two children with TBG deficiency were collected in the First Affiliated Hospital of College of Medicine, Zhejiang University. The related literature was searched form China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform, National Center for Biotechnology Information and PubMed (up to December 2015) by using search terms "Thyroxine binding globulin deficiency, gene, mutation" .

Result: Both patients were diagnosed as central hypothyroidism at the beginning and treated with L-thyroxine. Both of the identical twins of the triplet were observed for mutation in exon3, c. 631G﹥A(p.A211T), a new mutation had not been reported, but their parents and another non-identical triplet brother were normal. Literature review showed that 23 foreign cases with SERPINA7 gene mutation had been reported, however, no Chinese with SERPINA7 gene mutation had been reported. Among reported cases it was shown that SERPINA7 gene mutations located in exon, intron, promoter and enhancer. Up to now, 49 variants had been identified, 41 of them located in the mutated genes. Including these two cases, patients with thyroxine binding globulin deficiency were characterized by reduced serum TH levels, but normal free TH and TSH and absence of clinical manifestations.

Conclusion: The new mutation of SERPINA7 gene c. 631G﹥A(p.A211T)is not transmitted via the known X chromosome linked heredity, and as the cases were test tube triplet infants, it is a de novo mutation. The serum thyroid function tests of TBG deficiency showed decreased TT4, TT3 and normal TSH and TBG deficiency is often misdiagnosed as central hypothyroidism.