Should the GCM2 gene be tested when screening for familial primary hyperparathyroidism?

Objective: Primary hyperparathyroism (PHPT) is a disease with either sporadic or inherited presentation. Germline mutations responsible for this disease can be found in different genes, the most frequently involved being MEN1, CDC73 = HRPT2 and CASR. During the last few years, new genes have been described as responsible for the development of PHPT such as GCM2. These genes are not systematically included in PHPT genetic screening yet. The aim of this work was to assess the importance of GCM2 genetic analysis in PHPT to determine if this gene should be included in gene panel investigated for this disease.

Design And Methods: The TENGEN network (French Oncogenetic Network of Neuroendocrine Tumors) collected and interpreted allelic variants according to the clinical characteristics of the GCM2-positive patients identified through genetic testing performed in French laboratories (713 patients with PHPT).

Results: From 713 patients with PHPT included in this study, 85 (6.6%) carried at least one GCM2 variant. A total of 12 variants classified as uncertain significance or likely pathogenic were reported in 47 patients. Their mean age at PHPT diagnosis was 49 years. Additionally, the investigation of a large family showed that GCM2 variants could be associated with low penetrance.

Conclusion: We provide a description and interpretation for GCM2 variants identified in a French population. We suggest that this gene should be included in genetic screening of patients with PHPT and propose the follow-up of asymptomatic patients carrying such variants for calcemia.