We investigated the involvement of the HRPT2 gene by loss of heterozygosity analysis and direct sequencing in a kindred with hyperparathyroidism-jaw tumor syndrome (HPT-JT) and three kindreds with familial isolated primary hyperparathyroidism (FIHP). Seven patients with sporadic parathyroid cancers and 35 with parathyroid adenomas with no family history of primary hyperparathyroidism or HPT-JT were also studied. A germline heterozygous substitution G to A was found in the donor splice site of intron 1 in one of the three FIHP families. No mutations were identified in the HPT-JT kindred. A somatic HRPT2 mutation was found in four of seven patients with parathyroid cancers, two of which were unreported frameshift mutations (195insT and 195insA) in exon 2. Consistent with recent findings, two of seven patients with sporadic parathyroid cancer had germline mutations. Four adenomas showed loss of heterozygosity at HRPT2, whereas a somatic HRPT2 mutation was found in one. In conclusion, we provide additional evidence for a strong association between HRPT2 gene mutations and sporadic parathyroid cancer. The finding that two of the seven patients with sporadic parathyroid cancer carried an HRPT2 germline mutation suggests that they might have occult HPT-JT. Our results also confirm the need for testing HRPT2 gene in FIHP families.

Objective: HRPT2 gene mutations are associated with parathyroid carcinomas, and absence of parafibromin immunoreactivity has been suggested as a diagnostic marker of malignancy. The aim of our study was to extend parafibromin studies in a series of benign and malignant parathyroid tumors and cross-validate the results of immunohistochemistry with those of HRPT2 analysis. Design and patients: We performed parafibromin and cyclin D1 immunostaining and HRPT2 gene analysis using loss of heterozygosity studies and sequencing analysis in parathyroid specimens from 11 patients with carcinoma (eleven primary tumors, one skin, and four lung metastases), 22 with sporadic adenomas, and 4 with atypical adenomas. Results: Ten out of eleven parathyroid cancers were negative for parafibromin staining and showed HRPT2 gene abnormalities. The remaining sample was negative for immunostaining and genetic analyses. All but one sporadic adenomas showed parafibromin immunoreactivity and no HRPT2 gene abnormalities. The sample with negative immunostaining carried an HRPT2 mutation. Two atypical adenomas were positive and two negative with parafibromin staining. No HRPT2 abnormalities were found in these samples. Cyclin D1 expression was heterogeneous and there was no relationship between expression/expression level of cyclin D1 and parafibromin expression. Conclusions: We have shown that negative parafibromin staining is almost invariably associated with HRPT2 mutations and confirm that loss of parafibromin staining strongly predicts parathyroid malignancy. In clinical practice, these tests could be particularly useful in the subset of parathyroid tumors with equivocal histological examination. However, their diagnostic value in this setting remains to be proven.European Journal of Endocrinology 156 547-554

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy is a rare autosomal recessive disorder characterized by hypoparathyroidism, adrenal failure, chronic mucocutaneous candidiasis, and ectodermal dystrophies and other organspecific autoimmune diseases. Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy is caused by mutations of the autoimmune regulator gene.We identified an Italian family with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy and a pattern of inheritance suggestive of a dominant mechanism. Serological and clinical studies showed a high prevalence of hypothyroid autoimmune thyroiditis in affected members with classical autoimmune polyendocrinopathy-candidiasisectodermal dystrophy.Direct sequencing of the entire coding region of the autoimmune regulator gene revealed the presence in the proband of a novel missense (G228W) mutation in exon 6 in a heterozygous state. The same heterozygous mutation was identified in all family members with autoimmune polyendocrinopathycandidiasis-ectodermal dystrophy and/or hypothyroid autoimmune thyroiditis. None of the unaffected family members and 50 unrelated Italian controls carried the mutation.In contrast with all other autoimmune regulator mutations reported in families, the novel G228W mutation acts in a dominant fashion in our family, as only one heterozygous mutation was found in the entire coding sequence of the autoimmune regulator gene in the proband. Moreover, analysis of the family tree showed direct transmission of the hypothyroid autoimmune thyroiditis/polyendocrinopathy-candidiasis-ectodermal dystrophy phenotype to the offspring in each generation in the absence of consanguinity, further supporting a dominant inheritance. The G228W closely cosegregated with hypothyroid autoimmune thyroiditis in our family, whereas a low penetrance of the full autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy phenotype was observed.In conclusion, we report a novel mutation of the autoimmune regulator gene in a family with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, closely cosegregating with hypothyroid autoimmune thyroiditis. The

Inactivating mutations of the CDC73 tumor suppressor gene have been reported in parathyroid carcinomas (PC), in association with the loss of nuclear expression of the encoded protein, parafibromin. The aim of this study was to further investigate the role of the CDC73 gene in PC and evaluate whether gene carrier status and/or the loss of parafibromin staining might have an effect on the outcome of the disease. We performed genetic and immunohistochemical studies in parathyroid tumor samples from 35 patients with sporadic PC. Nonsense or frameshift CDC73 mutations were detected in 13 samples suitable for DNA sequencing. Six of these mutations were germline. Loss of parafibromin expression was found in 17 samples. The presence of the CDC73 mutation as well as the loss of parafibromin predicted a high likelihood of subsequent recurrence and/or metastasis (92.3%, P=0.049 and 94.1%, P=0.0017 respectively), but only the latter was associated with a decreased overall 5- and 10-year survival rates (59%, P=0.107, and 23%, P=0.0026 respectively). The presence of both the CDC73 mutation and loss of parafibromin staining compared with their absence predicted a lower overall survival at 10- (18 vs 84%, P=0.016) but not at 5-year follow-up. In conclusion, loss of parafibromin staining, better than CDC73 mutation, predicts the clinical outcome and mortality rate. The added value of CDC73 mutational analysis is the possibility of identifying germline mutations, which will prompt the screening of other family members.

Inactivation of the Rb1 gene is a common event in parathyroid tumorigenesis. Retention of heterozygosity seems to exclude parathyroid malignancy, which is suggested by the combined finding of LOH and lack of protein expression.