[Clinical and molecular features in a family with multiple endocrine neoplasia type-1 syndrome]

Mutational and large deletion study of genes implicated in hereditary forms of primary hyperparathyroidism and correlation with clinical features

The aim of this study was to carry out genetic screening of the MEN1, CDKN1B and AIP genes, both by direct sequencing of the coding region and multiplex ligation-dependent probe amplification (MLPA) assay in the largest monocentric series of Italian patients with Multiple Endocrine Neoplasia type 1 syndrome (MEN1) and Familial Isolated Hyperparathyroidism (FIHP). The study also aimed to describe and compare the clinical features of MEN1 mutation-negative and mutation-positive patients during long-term follow-up and to correlate the specific types and locations of MEN1 gene mutations with onset and aggressiveness of the main MEN1 manifestations. A total of 69 index cases followed at the Endocrinology Unit in Pisa over a period of 19 years, including 54 MEN1 and 15 FIHP kindreds were enrolled. Seven index cases with MEN1 but MEN1 mutation-negative, followed at the University Hospital of Cagliari, were also investigated. FIHP were also tested for CDC73 and CaSR gene alterations. MEN1 germline mutations were identified in 90% of the index cases of familial MEN1 (F-MEN1) and in 23% of sporadic cases (S-MEN1). MEN1 and CDC73 mutations accounted for 13% and 7% of the FIHP cohort, respectively. A CDKN1B mutation was identified in one F-MEN1. Two AIP variants of unknown significance were detected in two MEN1-negative S-MEN1. A MEN1 positive test best predicted the onset of all three major MEN1-related manifestations or parathyroid and gastro-entero-pancreatic tumors during follow-up. A comparison between the clinical characteristics of F and S-MEN1 showed a higher prevalence of a single parathyroid disease and pituitary tumors in sporadic compared to familial MEN1 patients. No significant correlation was found between the type and location of MEN1 mutations and the clinical phenotype. Since all MEN1 mutation-positive sporadic patients had a phenotype resembling that of familial MEN1 (multiglandular parathyroid hyperplasia, a prevalence of gastro-entero-pancreatic tumors and/or the classic triad) we might hypothesize that a subset of the sporadic MEN1 mutation-negative patients could represent an incidental coexistence of sporadic primary hyperparathyroidism and pituitary tumors or a MEN1 phenocopy, in our cohort, as in most cases described in the literature.

Clinical and Genetic Analysis of Multiple Endocrine Neoplasia Type 1-Related Primary Hyperparathyroidism in Chinese

Objective

Multiple endocrine neoplasia type 1-related primary hyperparathyroidism (MHPT) differs in many aspects from sporadic PHPT (SHPT). The aims of this study were to summarize the clinical features and genetic background of Chinese MHPT patients and compare the severity of the disease with those of SHPT.

Design and Methods

A total of 40 MHPT (27 sporadic, 7 families) and 169 SHPT cases of Chinese descent were retrospectively analyzed. X-rays and ultrasound were used to assess the bone and urinary system. Dual energy x-ray absorptiometry (DXA) were performed to measure bone mineral density (BMD). Besides direct sequencing of the MEN1 and CDKN1B genes, multiplex ligation-dependent probe amplification (MLPA) was used to screen gross deletion for the MEN1 gene.

Results

Compared with SHPT patients, MHPT patients showed lower prevalence of typical X-ray changes related to PHPT (26.3% vs. 55.7%, P = 0.001) but higher prevalence of urolithiasis/renal calcification (40.2% vs. 60.0%, P = 0.024). MHPT patients showed higher phosphate level (0.84 vs. 0.73mmol/L, P<0.05) but lower ALP (103.0 vs. 174.0U/L, P<0.001) and PTH (4.0 vs. 9.8×upper limit, P<0.001) levels than SHPT patients. There were no significant differences in BMD Z-scores at the lumbar spine and femoral neck between the two groups. Mutations in the MEN1 gene were detected in 27 MHPT cases. Among the nine novel mutations were novel, one of them involved the deletion of exon 5 and 6.

Conclusions

MHPT patients experienced more common kidney complications but less skeletal issues, and a milder biochemical manifestation compared with SHPT patients. MEN1 mutation detection rate was 79.4% and 9 of the identified mutations were novel.

Deletion of exons 1-3 of the MEN1 gene in a large Italian family causes the loss of menin expression

Multiple endocrine neoplasia type 1 (MEN1) syndrome is an autosomal dominant disease, characterized by parathyroid adenomas, endocrine gastroenteropancreatic tumors and pituitary adenomas, due to inactivating mutations of the MEN1 gene (chromosome 11q13). MEN1 mutations are mainly represented by nonsense, deletions/insertions, splice site or missense mutations that can be detected by direct sequencing of genomic DNA. However, MEN1 patients with large heterozygous deletions may escape classical genetic screening and may be misidentified as phenocopies, thereby hindering proper clinical surveillance. We employed a real-time polymerase chain reaction application, the TaqMan copy number variation assay, to evaluate a family in which we failed to identify an MEN1 mutation by direct sequencing, despite a clear clinical diagnosis of MEN1 syndrome. Using the TaqMan copy number variation assay we identified a large deletion of the MEN1 gene involving exons 1 and 2, in three affected family members, but not in the other nine family members that were to date clinically unaffected. The same genetic alteration was not found in a group of ten unaffected subjects, without family history of endocrine tumors. The MEN1 deletion was further confirmed by multiplex ligation-dependent probe amplification, which showed the deletion extended from exon 1 to exon 3. This new approach allowed us to correctly genetically diagnose three clinical MEN1 patients that were previously considered as MEN1 phenocopies. More importantly, we excluded the presence of genetic alterations in the unaffected family members. These results underline the importance of using a variety of available biotechnology approaches when pursuing a genetic diagnosis in a clinically suggestive setting of inherited endocrine cancer.