Germline Mutations Related to Primary Hyperparathyroidism Identified by Next-Generation Sequencing

The Role of Demographic and Clinical Factors in Germline Mutation Testing for Patients with Primary Hyperparathyroidism

INTRODUCTION

Guidelines recommending genetic counseling in primary hyperparathyroidism (PHPT) vary. To further delineate current recommendations, this study examined genetic counseling referral patterns and rates of mutations in surgical patients with PHPT.

PATIENTS AND METHODS

A single-institution review was performed of adult patients who underwent parathyroidectomy for presumed sporadic PHPT. Genetic testing indications of hypercalcemia onset ≤ 40 years, multigland disease (MGD), family history (FHx) of PHPT, or other clinical indications suspicious for a PHPT-related endocrinopathy were examined by demographics and mutation detection rates.

RESULTS

Genetic counseling was performed in 237 (37.9%) of 625 patients. Counseling was discussed but not performed in 121 (19.4%) patients. No evidence was noted of genetic referral discussion in the remaining 267 (42.7%). Of these groups, patients who received genetic counseling were youngest, p < 0.001 [median age 55.3 (IQR 43.2, 66.7) years]. The majority of patients with indications of age ≤ 40 years (65.7%), FHx (78.0%), and other clinical indications (70.7%) underwent genetic counseling, while most with MGD (57.0%) did not. Eight mutations were detected in 227 patients (3.5%). Mutations included: MEN1 (n = 2), CDC-73 (n = 4), and CASR (n = 2). Detection was most common in patients with FHx (4/71, 5.6%), then age ≤ 40 years (3/66, 4.5%), and other clinical indications (3/80, 3.8%). No mutations were identified in 48 patients tested solely for MGD.

CONCLUSIONS

Most patients with onset of hypercalcemia age ≤ 40 years, positive FHx, or other clinical concerns underwent genetic counseling, while most with MGD did not. As no germline mutations were identified in patients with MGD alone, further investigation of MGD as a sole indication for genetic counseling may be warranted.

Overview of Thyroid and Parathyroid Disease-The Endocrinology Perspective

Thyroid and parathyroid disorders are quite common in the population and range from benign to malignant conditions that may be hormonally active or inactive. Select disorders of the thyroid and parathyroid can be managed medically, although there are a variety of circumstances that may require definitive management with surgery. Surgical intervention may be required for hormonal control, compressive symptoms, or for the removal and/or control of malignancy. The endocrinologist's perspective of the preoperative and postoperative management regarding thyroid and parathyroid surgeries will be discussed.

Molecular Genetic Aspects of Sporadic Multiglandular Primary Hyperparathyroidism

Multiglandular primary hyperparathyroidism (MGD) represents a rare form of primary hyperparathyroidism (PHPT). MGD is associated with hereditary PHPT, but the sporadic MGD is more common and affects a similar patient profile as single gland parathyroid disease (SGD). The distinction between SGD and MGD is of great clinical importance, especially for the strategy of parathyroidectomy. Based on the limited knowledge available, MGD is likely to be a genetically heterogeneous disease resulting from the interaction of germline and somatic DNA mutations together with epigenetic alterations. Furthermore, these events may combine and occur independently in parathyroid tumors within the same individual with MGD. Gene expression profiling has shown that SGD and MGD may represent distinct entities in parathyroid tumorigenesis. We are waiting for studies to analyze exactly which genes are different in SGD and MGD in order to identify potential biomarkers that can distinguish between the two forms of the disease.

Expert consensus on multidisciplinary approach to the diagnosis and treatment of primary hyperparathyroidism in pregnancy in China

Primary hyperparathyroidism in pregnancy is a rare disease that can have detrimental effects on both maternal and fetal/neonatal outcomes. The physiological changes that occur during pregnancy can complicate the diagnosis, imaging examinations, and treatment of this disorder. To enhance our understanding and management of primary hyperparathyroidism in pregnancy, experts from various fields, including endocrinology, obstetrics, surgery, ultrasonography, nuclear medicine, pediatrics, nephrology, and general practice in China, collaborated to develop a consensus addressing the critical aspects of the diagnosis and treatment of primary hyperparathyroidism in pregnancy with a multidisciplinary team approach. This consensus provides valuable guidance for healthcare professionals in managing this condition, ultimately improving outcomes for both mothers and their babies.

A Knock-In Mouse Model of the Gcm2 Variant p.Y392S Develops Normal Parathyroid Glands

Context

The glial cells missing 2 (GCM2) gene functions as a transcription factor that is essential for parathyroid gland development, and variants in this gene have been associated with 2 parathyroid diseases: isolated hypoparathyroidism in patients with homozygous germline inactivating variants and primary hyperparathyroidism in patients with heterozygous germline activating variants. A recurrent germline activating missense variant of GCM2, p.Y394S, has been reported in patients with familial primary hyperparathyroidism.

Objective

To determine whether the GCM2 p.Y394S missense variant causes overactive and enlarged parathyroid glands in a mouse model.

Methods

CRISPR/Cas9 gene editing technology was used to generate a mouse model with the germline heterozygous Gcm2 variant p.Y392S that corresponds to the human GCM2 p.Y394S variant. Wild-type (Gcm2+/+) and germline heterozygous (Gcm2+/Y392S) mice were evaluated for serum biochemistry and parathyroid gland morphology.

Results

Gcm2 +/Y392S mice did not show any change compared to Gcm2+/+ mice in serum calcium and parathyroid hormone levels, parathyroid gland histology, cell proliferation, or parathyroid gland size.

Conclusion

The mouse model of the p.Y392S variant of Gcm2 shows that this variant is tolerated in mice, as it does not increase parathyroid gland cell proliferation and circulating calcium or PTH levels. Further investigation of Gcm2+/Y392S mice to study the effect of this variant of Gcm2 on early events in parathyroid gland development will be of interest.

Brown tumor due to primary hyperparathyroidism in a familial case: a case report

BACKGROUND

Primary hyperparathyroidism (PHPT) is an uncommon disorder characterised by hypercalcemia with an increased parathyroid hormone level. We reported a PHPT familial case with two subjects, a father and a daughter, and both of them had suffered from the brown tumor.

CASE PRESENTATION

The proband, a 43-year-old patient, developed parathyroid adenomas at the age of 15; a histologically confirmed right parathyroid adenoma was removed by parathyroidectomy; and after six months follow-up, the serum calcium level was normalised. At the age of thirty-three, a CT scan of his head and neck revealed a mass in the right maxilla, as well as PHPT (i.e., left inferior parathyroid adenoma). Then, he underwent a biopsy of an exophytic lesion in the right maxilla and was diagnosed by pathology as a brown tumor, with the serum calcium and PTH levels at 2.78 mmol/L and 221 pg/mL, respectively. Subsequently, the patient took a left inferior parathyroid microwave ablation with ultrasound guidance. After three months of follow-up, the serum calcium and PTH levels returned to normal, and the brown tumor was resolved. After three years, it mineralised as revealed in a CT scan. By the time he was 43 years old, during the 28-year follow-up period, the serum calcium and PTH levels were still within the normal range, and there was no discomfort reported. He has consistently taken calcium supplements throughout the 28 years. Since the initial diagnosis, his blood indicators of kidney function have been normal, and ultrasound showed renal calculus in the right kidney and a normal left kidney. The proband's daughter, a 15-year-old girl, experienced left upper extremity pain for ten months. CT scan revealed a mass in the distal left radius, and a giant cell tumor was suspected. A surgical internal fixation was performed, and the pathology showed a brown tumor. Laboratory tests revealed a serum parathyroid hormone (PTH) level of 1554pg/mL, calcium level of 3.14 mmol/L, phosphorus level of 0.72 mmol/L, and alkaline phosphatase level of 1892 U/L. Given the osteitic changes and elevated levels of calcium and PTH, ultrasonography was performed, after which a mass was detected measuring 19 × 9 × 7 mm mixed with solid components and cystic fluid in the right thyroid gland. The results of 99mTc-MIBI scintigraphy confirmed the abnormal accumulation of 99mTc-MIBI in the right thyroid gland but not seen in the bilateral parathyroid glands. The patient underwent thyroidectomy, and the postoperative pathology report indicated an intra-thyroid ectopic parathyroid adenoma. The serum calcium and PTH levels became normal at 4 h after surgery. One to three months after operation, the serum calcium level was low, while the serum PTH level was high. Then, the patient was advised to take calcium supplements. Until the sixth month after the operation, the serum calcium level and serum PTH level returned to normal, and the bone pain was relieved. The patient's blood tests for kidney function remained normal. There was no evidence of bilateral kidney disease (such as nephrolithiasis or nephrocalcinosis) detected by ultrasound scan. There were several similarities in the state of illness between these two subjects. Both the father and the daughter developed parathyroid adenomas at the age of 15, and there was no lesion in other endocrine glands. And genetic testing revealed mutations in the CDC73 genes in both father and daughter. On the other hand, there were also a few differences. The father's first signs of brown tumor were in the right maxilla, while the daughter's appeared in the distal left radius. The father presented pathological changes in the left and right parathyroid glands, whereas the daughter presented with an ectopic parathyroid adenoma in the right thyroid gland.

CONCLUSION

We report a familial case in which father and daughter were diagnosed to have brown tumors due to parathyroid adenoma and ectopic parathyroid adenoma, and genetic testing revealed CDC73 gene mutations in both. Therefore, in the diagnostic and differential process of young patients having bone disease, clinicians should not only focus on the clinical manifestations of the skeleton, but also implement a comprehensive analysis of systemic symptoms, considering the possibility that the patient has familial PHPT.

Parathyroid carcinoma: molecular therapeutic targets

Parathyroid carcinoma (PC) is an extremely rare malignant tumor of the parathyroid glands, accounting for less than 1% of primary hyperparathyroidism, commonly characterized by severe and unmanageable hypercalcemia, aggressive behavior, high metastatic potential, and poor prognosis. PC manifests prevalently as a sporadic tumor and only occasionally it is part of congenital syndromic and non-syndromic endocrine diseases. Molecular pathogenesis of this form of parathyroid tumor is not fully elucidated and it appears to be caused by multiple genetic and epigenetic drivers, differing among affected patients and not yet clearly stated in distinguishing PC from the benign parathyroid adenoma (PA). Congenital forms of PC have been prevalently associated with germline heterozygous loss-of-function mutations of the CDC73 tumor suppressor gene, both in the context of the hyperparathyroidism jaw-tumor syndrome (HPT-JT) and of the isolated familial hyperparathyroidism (FIPH). Currently, surgical en bloc resection of affected gland(s) and other involved structures is the elective therapy for both primary and recurrent PC. However, it usually results ineffective for advance and metastatic disease, and a high percentage of post-operative recurrence is reported. Targeted medical therapies for surgically untreatable PC, based on the molecular profile of PC samples, are, therefore, needed. The characterization of genetic and epigenetic alterations and deregulated pathways in PC samples will be of fundamental importance to tailor treatment for each patient. Here, we reviewed main findings on molecular pathogenetic aspects of PC, and the current state of the art of therapies.

Genetic and clinical screening for hereditary primary hyperparathyroidism in a large Chinese cohort: a single-center study

Primary hyperparathyroidism (PHPT) includes sporadic PHPT and hereditary PHPT. However, until now, there have been no exact data on the proportion and composition of hereditary PHPT in the Chinese PHPT population. This study aimed to clarify the proportion and composition of hereditary PHPT in patients at a large academic center in Beijing, China, and to analyze genotype-phenotype characteristics. A total of 394 newly diagnosed Han PHPT patients who consented to genetic screening were enrolled. Targeted next-generation sequencing (T-NGS) (including for MEN1, RET, CDKN1B, CaSR, HRPT2/CDC73, GNA11, AP2S1, GCM2), combined with MEN1-multiplex ligation-dependent probe amplification (MLPA) and CDC73-MLPA, was used for genetic screening. Diagnosis of hereditary PHPT was based on clinical manifestations, family history, and genetic screening. Thirty-seven pathogenic (P)/likely pathogenic (LP) variants were detected in 41 patients via T-NGS, and three patients carried long-range deletions of MEN1 or CDC73 detected by MLPA, with a variant detection rate of 11.2% (44/394). In total, 30 patients were clinically diagnosed with MEN1. Combined with genetic and clinical screening, the rate of hereditary PHPT in this study was 18.8% (74/394). For purposes of comparison, the rate of unequivocal nonhereditary PHPT was 66.5% (262/394); 14.7% (58/394) did not exhibit the clinical features of hereditary PHPT but carried variants of uncertain clinical significance and so could not be clearly categorized. Both the age at hospital visit (43.6 ± 14.0 versus 53.7 ± 14.9 years) and age at onset (35.4 ± 13.8 versus 50.6 ± 14.8 years) in the hereditary group (n = 74) were significantly lower than those in the nonhereditary group (n = 262). Higher levels of ionized calcium and serum β-CTX were observed in the hereditary group; proportions of parathyroid hyperplasia and multigland involvement were also higher. In addition to multigland disease and positive family history, it is recommended that patients with an age of onset less than 38 should be screened for hereditary forms. © 2023 American Society for Bone and Mineral Research (ASBMR).

Sporadic parathyroid adenoma: an updated review of molecular genetics

Introduction

Primary HPT (PHPT) is a common disorder, affecting approximately 1% of the general population. Parathyroid adenomas emerge as non-familial sporadic in 90% of cases. The aim of this review is to give a detailed update of molecular genetics of sporadic parathyroid adenoma reported in international literature.

Methods

A bibliographic research was conducted in PubMed, Google Scholar, and Scopus.

Results

Seventy-eight articles were included in our review. CaSR, MEN1, CCND1/PRAD, CDKI, angiogenic factors like VEGF, FGF, TGFβ, and IGF1, and apoptotic factors are important genes in parathyroid adenomas pathogenesis that have been established by several studies. A huge list of proteins is differently expressed in parathyroid adenomas measured by Western Blotting, MALDI/TOF, MS spectrometry, and immunohistochemistry. These proteins take part in several cell processes such as cell metabolism, cytoskeleton structural stability, cell oxidative stress regulation, cell death, transcription, translation, cell connection, and cell signaling transmission, while they can be found over- or underexpressed in abnormal tissues.

Conclusion

This review gives a detailed analysis of all reported data on genomics and proteomics of parathyroid adenoma. Further studies should be applied on understanding parathyroid adenoma pathogenesis and introducing new biomarkers for early detection of primary hyperparathyroidism.

Parathyroid Carcinoma: Update on Pathogenesis and Therapy

Parathyroid carcinoma (PC) is a very rare endocrine cancer with aggressive behavior, a high metastatic potential, and a poor prognosis. Surgical resection of affected gland(s) and other involved structures is the elective therapy. Pre-operative and intra-operative differential diagnosis with benign parathyroid adenoma remains a challenge. The lack of a clear pre-operative diagnosis does not allow one, in many cases, to choose the correct surgical approach to malignant PC, increasing persistence, the recurrence rate, and the risk of metastases. An initial wrong diagnosis of parathyroid adenoma, with a minimally invasive parathyroidectomy, is associated with over 50% occurrence of metastases after surgery. Genetic testing could help in identifying patients at risk of congenital PC (i.e., CDC73 gene) and in driving the choice of neck surgery extension. Targeted effective treatments, other than surgery, for advanced and metastatic PC are needed. The pathogenesis of malignant parathyroid carcinogenesis is still largely unknown. In the last few years, advanced molecular techniques allowed researchers to identify various genetic abnormalities and epigenetic features characterizing PC, which could be crucial for selecting molecular targets and developing novel targeted therapeutic agents. We reviewed current findings in PC genetics, epigenetics, and proteomics and state-of-the-art therapies.

Advances and Updates in Parathyroid Pathology

Hyperparathyroidism is a common endocrine disorder characterized by elevated levels of parathyroid hormone and hypercalcemia and is divided into 3 types: primary, secondary, and tertiary. Distinction between these types is accomplished by correlation of clinical, radiologic, and laboratory findings with pathologic features. Primary hyperparathyroidism occurs sporadically in 85% of cases with the remaining cases associated with multiple familial syndromes. The pathologic manifestations of primary hyperparathyroidism include parathyroid adenoma, parathyroid hyperplasia, and parathyroid carcinoma. Recent advances in the understanding of the pathogenesis of parathyroid disease has helped to refine the diagnosis and classification of parathyroid lesions. The identification of multiple clonal proliferations in traditional multiglandular parathyroid hyperplasia has led to the adoption by the World Health Organization (WHO) of the alternate term of primary hyperparathyroidism-related multiglandular parathyroid disease. Additional nomenclature changes include the adoption of the term atypical parathyroid tumor in lieu of atypical parathyroid adenoma to reflect the uncertain malignant potential of these neoplasms. Clinical and morphologic features characteristic of familial disease have been described that can help the practicing pathologist identify underlying familial disease and provide appropriate management. Use of ancillary immunohistochemistry and molecular studies can be helpful in classifying parathyroid neoplasms. Parafibromin has proven useful as a diagnostic and prognostic marker in atypical parathyroid tumors and parathyroid carcinomas. This review provides an update on the diagnosis and classification of parathyroid lesions considering the recent advances in the understanding of the molecular and clinical features of parathyroid disease and highlights the use of ancillary studies (immunohistochemical, and molecular) to refine the diagnosis of parathyroid lesions.

The SLC6A19 gene mutation in a young man with hyperglycinuria and nephrolithiasis: a case report and literature review

BACKGROUND

Hyperglycinuria is a rare disorder, with few reported cases, caused by either a defect in glycine metabolism or a disturbance in renal glycine reabsorption. Genetic findings of hyperglycinuria are rare and have not previously been reported in Chinese young men.

CASE PRESENTATION

A 24-year-old man presented with a compliant of bilateral lumbago for 1 month. Abdominal computed tomography revealed bilateral kidney stones and right upper ureteral dilatation. The 24-h urine analysis showed high urine oxalate levels of 63 mg/day. Analysis of amino acids in urine revealed that his urinary glycine levels were abnormally high (2.38 µmol/mg creatinine). Whole-exome sequencing detected the SLC6A19 variant c.1278 C > T p. (Cys426). Flexible ureteroscopy with holmium laser lithotripsy was conducted twice to remove his bilateral nephrolithiasis. Postoperative stone biochemical composition analysis revealed that the stones were composed of approximately 70% calcium oxalate monohydrate and 30% calcium oxalate dihydrate. The patient was subsequently diagnosed with hyperglycinuria. Three months after the stone surgery, ultrasonography revealed one nodule under the right thyroid lobe during a health checkup. His serum parathyroid hormone (PTH) levels increased to 392.3 pg/mL. Resection of the right parathyroid nodule was performed, and the histopathological examination confirmed right parathyroid adenoma. During the 2-year follow-up period, nephrolithiasis did not relapse, and serum PTH, calcium, and phosphorus levels were normal.

CONCLUSION

The SLC6A19 gene may have been significant in the development of hyperglycinuria in a Chinese young man. Further evaluation for the possibility of a glycine excretion disorder could be considered when encountering nephrolithiasis.