Pseudohypoparathyroidism (PHP) is a rare disorder caused by genetic and epigenetic aberrations in the GNAS complex locus resulting in impaired expression of stimulatory G protein (Gsα). PHP type Ib (PHP-Ib) is characterized by hypocalcemia and hyperphosphatemia due to renal resistance to the parathyroid hormone, and is distinguished from PHP-Ia by the absence of osteodystrophic features. An 11-yr-old boy presented with poor oral intake and cramping lower limb pain after physical activity. Laboratory studies revealed hypocalcemia, hyperphosphatemia, and increased parathyroid hormone levels. The GNAS complex locus was evaluated using the methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) assay. Gain of methylation in the NESP55 domain and loss of methylation in the antisense (AS) transcript, XL, and A/B domains in the maternal allele were observed. Consequently, we present a case of PHP-Ib diagnosed using MS-MLPA.
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Case Report
A Case of Pseudohypoparathyroidism Type Ib Caused by Aberrant Methylation in the GNAS Complex Locus
1Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2Department of Pediatrics, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Received: June 13, 2016; Revised: August 17, 2016; Accepted: August 18, 2016
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Lab Med Online 2017; 7(2): 83-87
Published April 1, 2017 https://doi.org/10.3343/lmo.2017.7.2.83
Copyright © The Korean Society for Laboratory Medicine.