The purpose of this study was to investigate the underlying HRPT2 defect in a young patient with symptomatic hyperparathyroidism due to an apparently sporadic parathyroid adenoma with cystic features.
Mutations in the hyperparathyroidism type 2 (HRPT2/CDC73) gene and alterations in the parafibromin protein have been established in the majority of parathyroid carcinomas and in subsets of parathyroid adenomas.
Genetic analysis of the CDC73 gene [for Hyperparathyroidism-jaw tumor (HPT-JT)], MEN1 for Multiple Endocrine Neoplasia Type1, CDKN1B for MEN4, SDHB and SDHD for Paraganglioma/Pheochromocytoma susceptibility, VHL for von Hippel-Lindau Syndrome, BMPR1A and SMAD4 for Juvenile Polyposis Syndrome (JPS) (sequencing and MLPA), karyotype and array CGH (44 K) were all normal.
In 2002, germline HRPT2 (also known as CDC73) mutation was reported as the cause of hyperparathyroidism-jaw tumor (HPT-JT) syndrome, an autosomal dominant hereditary tumor syndrome associated with a lifetime risk of parathyroid carcinoma approaching 15 %.
This case illustrates that the hyperparathyroidism and the fibro-osseous tumors are independent features of the persistent germline tumor suppressor gene (CDC73) mutation.
We briefly review published childhood cases, consider the challenges in differentiating malignant from benign hyperparathyroidism in this age group, and discuss the association of CDC73 mutations with parathyroid carcinoma.
Screening for the mutated CDC73 confirmed carrier status in the proband's daughter and the biochemistry and ultrasonography led to pre-emptive surgery and resolution of the hyperparathyroidism.
The phenotypes and outcome of MEN1-, MEN4- and HRPT2-related HPTH are briefly described, with a focus on the most recent literature data and is compared with familial hypocalciuric hypercalcemia.
<i>Parathyroid carcinoma.</i> Most parathyroid carcinomas are functional, resulting in hyperparathyroidism and a high serum calcium level; however, non-functioning parathyroid carcinomas are also rarely described in individuals with a <i>CDC73-</i>related disorder.