[Pseudohypoparathyroidism and GNAS gene defects: clinical evaluation and molecular analysis in 20 children]

Objective: To analyze the patients' clinical and genetic characteristics with pseudohypoparathyroidism (PHP) and investigate the correlation between clinical phenotypes and genotypes. Methods: Twenty PHP patients were ascertained at Children's Hospital Zhejiang University School of Medicine from January 2011 to July 2020. Clinical manifestation, laboratory examination and gene test results were retrospectively analyzed. Results: In these twenty patients, eighteen cases showed resistance to parathyroid hormone (PTH) and thirteen cases had Albright's hereditary osteodystrophy (AHO) phenotype. Gene abnormalities were found in all the twenty PHP patients, which included seven patients with GNAS gene variations (six frameshifts and one missense) and thirteen patients with GNAS gene methylation defects. Moreover, twelve children with both PTH resistance and AHO phenotype were clinically diagnosed as PHP-Ⅰa, meanwhile, seven carried GNAS variations and five had methylation abnormalities with a correct diagnosis of PHP-Ⅰb. Conclusions: Patients with AHO phenotype and PTH resistance may have a high genetic diagnosis rate. Because PHP-Ⅰb clinical phenotype may be similar to PHP-Ⅰa, early genetic detection is required for the differential diagnosis. In addition, children without PTH resistance should also be followed up regularly, which may help the early diagnosis.