Genetic Screening in a Large Chinese Cohort of Childhood Onset Hypoparathyroidism by Next-Generation Sequencing Combined with TBX1-MLPA.

At least 15 candidate genes have been implicated in hypoparathyroidism (HP). However, comprehensive screening of causative genes for HP is lacking. Here, we investigated the genotype spectrum in a large group of Chinese patients with childhood onset HP. A total of 173 patients with childhood onset HP were analyzed using targeted next-generation sequencing (NGS), including 15 candidate genes combined with multiplex ligation-dependent probe amplification (MLPA) of the TBX1 gene. Twenty-seven pathogenic or likely pathogenic mutations in five genes (TBX1, AIRE, GATA3, FAM111A, and CASR) including 13 novel variants in 23 patients, and 12 variants of uncertain clinical significance in five genes (GATA3, CASR, FAM111A, GCM2, and PTH) in 11 patients, were identified by NGS. Additionally, an entire gene deletion of TBX1 in 25 patients was found by TBX1-MLPA. Combined with clinical data, 26 (15.0%) cases of DiGeorge syndrome (OMIM #188400), nine (5.2%) autoimmune polyglandular syndrome type 1 (OMIM #240300), eight (4.6%) autosomal dominant hypocalcemia type 1 (OMIM #601198), four (2.3%) hypoparathyroidism-deafness-renal dysplasia syndrome (OMIM #146255), and one (0.6%) Kenny-Caffey syndrome type 2 (OMIM #127000) were verified. Among them, 16 of 26 (61.5%) DiGeorge syndrome cases were undiagnosed due to the lack of obvious clinical clues before genetic testing. The onset age of patients with mutations (median [interquartile range], 2.8 [0.1, 9.6] years) was significantly earlier than those without mutations (13.0 [8.8, 15.0] years) (p < 0.001). Family history, early onset age, especially prior to 5 years old, and extraparathyroid manifestations were clues for hereditary HP. The combined targeted NGS and TBX-1 MLPA were conveniently and effectively used for comprehensive genetic screening in this large Chinese cohort of childhood onset HP patients. Genetic defects were identified in 27.7% of early-onset HP patients, including four kinds of syndromic HP and one isolated HP. A total of 13 novel mutations were detected, which expands the mutation spectrum of hypoparathyroidism.