Novel 4.18 Mb deletion resulting in 2q37 microdeletion syndrome combined with PTH resistance found in one Chinese patient

Abstract

Background: 2q37 microdeletion syndrome is a rare clinical condition characterized by a series of physical abnormalities. Its Albright hereditary osteodystrophy (AHO)-like manifestations and possible complication of biochemical abnormalities indicating PTH resistance greatly increased the likelihood of misdiagnosis with classic pseudohypoparathyroidism (PHP) caused by GNAS mutation or methylation alteration, even though there have only been six reports of such clinical occasions.

Purpose: to investigate the underlying genetic defect in a male patient presenting hypocalcemia, elevated PTH and with a history of kyphosis.

Method: clinical information was collected, while the DNA was extracted from peripheral blood and subjected to methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and exome sequencing.

Result: Physical characteristics featuring short stature, obesity, round face, short neck, and shortened 4^th metacarpal and laboratory examination of the patient suggested the presence of PTH resistance, which is indicative of PHP. MS-MLPA did not reveal methylation alterations or deletions of GNAS, STX16 or other monogenetic alterations responsible for iPPSDs, but WES revealed a long-range deletion of approximately 4.18 Mb of the 2q37 region that spanned AGAP1 to NDUFA10, indicating that the patient had 2q37 microdeletion syndrome with PTH resistance.

Conclusion: After undergoing MS-MLPA and exome sequencing, a novel deletion spanning 4.18 Mb on the 2q37 region was identified in one male patient, clarifying the diagnosis of 2q37 microdeletion syndrome with PTH resistance. The new genetic discovery added to our understanding of the molecular defects that cause inactivating PTH/PTH-related protein signaling disorders (iPPSDs).

Keywords: 2q37 microdeletion syndrome; MS-MLPA; PTH resistance; exome sequencing; pseudohypoparathyroidism.