Congenital Central Hypothyroidism Caused by a Novel Thyroid-Stimulating Hormone-Beta Subunit Gene Mutation in Two Siblings.

Congenital central hypothyroidism (CCH) is a very rare disease. Alterations in pituitary development genes as well as mutations of immunoglobulin superfamily member 1 and transducin ß-like protein 1 can result in CCH and multiple pituitary hormone deficiencies. However, mutations of the thyrotropin-releasing hormone receptor or thyroid-stimulating hormone-beta (TSHB) gene are responsible for isolated CCH. In this paper, we present the cases of two siblings with a novel mutation of TSHB. Direct sequencing of the coding regions and exon/intron boundaries of the TSHB gene revealed two homozygous nucleotides changes. One of them was c.40A>G (rs10776792) which is a very common variation that is also seen in healthy individuals, the other was c.94G>A at codon 32 of exon 2 which resulted in a change from glutamic acid to lysine (p.E32K). Both patients were homozygous and the parents were heterozygous.

Molecular spectrum and differential diagnosis in patients referred with sporadic or autosomal recessive osteogenesis imperfecta.

BACKGROUND: Osteogenesis imperfecta (OI) is a heterogeneous bone disorder characterized by recurrent fractures. Although most cases of OI have heterozygous mutations in COL1A1 or COL1A2 and show autosomal dominant inheritance, during the last years there has been an explosion in the number of genes responsible for both recessive and dominant forms of this condition. Herein, we have analyzed a cohort of patients with OI, all offspring of unaffected parents, to determine the spectrum of variants accounting for these cases. Twenty patients had nonrelated parents and were sporadic, and 21 were born to consanguineous relationships. METHODS: Mutation analysis was performed using a next-generation sequencing gene panel, homozygosity mapping, and whole exome sequencing (WES). RESULTS: Patients offspring of nonconsanguineous parents were mostly identified with COL1A1 or COL1A2 heterozygous changes, although there were also a few cases with IFITM5 and WNT1 heterozygous mutations. Only one sporadic patient was a compound heterozygote for two recessive mutations. Patients offspring of consanguineous parents showed homozygous changes in a variety of genes including CRTAP,FKBP10,LEPRE1,PLOD2,PPIB,SERPINF1,TMEM38B, and WNT1. In addition, two patients born to consanguineous parents were found to have de novo COL1A1 heterozygous mutations demonstrating that causative variants in the collagen I structural genes cannot be overlooked in affected children from consanguineous couples. Further to this, WES analysis in probands lacking mutations in OI genes revealed deleterious variants in SCN9A,NTRK1, and SLC2A2, which are associated with congenital indifference to pain (CIP) and Fanconi-Bickel syndrome (FBS). CONCLUSION: This work provides useful information for clinical and genetic diagnosis of OI patients with no positive family history of this disease. Our data also indicate that CIP and FBS are conditions to be considered in the differential diagnosis of OI and suggest a positive role of SCN9A and NTRK1 in bone development.