Clinical and Genetic Characteristics of Pseudohypoparathyroidism in the Chinese Population

Summary

Background

Pseudohypoparathyroidism (PHP) is caused by mutations and epimutations in the GNAS locus, and characterized by the possibility of resistance to multiple hormones and Albright's hereditary osteodystrophy. PHP can be classified into the forms 1A/C, sporadic 1B, and familial 1B.

Objectives

To obtain an overall view of the clinical and genetic characteristics of the Chinese PHP patient population.

Methods

From 2000 to 2016, 120 patients were recruited and studied using Sanger sequencing, methylation-specific multiple ligation-dependent probe amplification (MS-MLPA), and combined bisulfiterestriction analysis (COBRA). Of these patients, 104 had positive molecular alterations indicative of certain forms of PHP and were included in data analysis. Clinical and laboratory features were compared between PHP1A/C and PHP1B patients.

Results

Ten PHP1A/C, 21 familial PHP1B, and 73 sporadic PHP1B patients were identified. Four novel GNAS mutations were discovered in these patients, including c.1038+1G>T, c.530+2T>C, c.880_883delCAAG, and c.311_312delAAG,insT. The most common symptoms in this series were recurrent tetany (89.4%) and epilepsy (47.1%). The prevalence of weight excess increased with age for PHP1B (10-35%) and PHP1A/C (50-75%). Intracranial calcification had a prevalence of 94.6% and correlated with seizures (r=0.227, p=0.029). Cataracts occurred in 56.2% PHP patients, and there was a trend towards longer disease duration in patients with cataracts (p=0.051). Statistically significant differences (p<0.05) were observed when comparing certain clinical characteristics between PHP1B and PHP1A/C patients, including age of onset (10yr vs. 7yr), short stature (21.3 vs. 70%), rounded face (60.6 vs. 100%), brachydactyly (25.5 vs. 100%), ectopic ossification (1.1 vs. 40%), and TSH resistance (44.6 vs. 90%), respectively.

Conclusions

This study is the largest single-centre series of PHP patients and summarises the clinical and genetic features of the Chinese PHP population. While there was substantial clinical overlap between PHP1A/C and PHP1B, differences in disease progression were observed.

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