[Germline mutations in the MEN1 gene: basis for predictive genetic screening and clinical management of multiple endocrine neoplasia type 1 (MEN1) families]

Multiple endocrine neoplasia type 1: analysis of germline MEN1 mutations in the Italian multicenter MEN1 patient database

PURPOSE

Multiple endocrine neoplasia type 1 (MEN1) is caused by germline inactivating mutations of the MEN1 gene. Currently, no direct genotype-phenotype correlation is identified. We aim to analyze MEN1 mutation site and features, and possible correlations between the mutation type and/or the affected menin functional domain and clinical presentation in patients from the Italian multicenter MEN1 database, one of the largest worldwide MEN1 mutation series published to date.

METHODS

The study included the analysis of MEN1 mutation profile in 410 MEN1 patients [370 familial cases from 123 different pedigrees (48 still asymptomatic at the time of this study) and 40 single cases].

RESULTS

We identified 99 different mutations: 41 frameshift [small intra-exon deletions (28) or insertions (13)], 13 nonsense, 26 missense and 11 splicing site mutations, 4 in-frame small deletions, and 4 intragenic large deletions spanning more than one exon. One family had two different inactivating MEN1 mutations on the same allele. Gastro-entero-pancreatic tumors resulted more frequent in patients with a nonsense mutation, and thoracic neuroendocrine tumors in individuals bearing a splicing-site mutation.

CONCLUSIONS

Our data regarding mutation type frequency and distribution are in accordance with previously published data: MEN1 mutations are scattered through the entire coding region, and truncating mutations are the most common in MEN1 syndrome. A specific direct correlation between MEN1 genotype and clinical phenotype was not found in all our families, and wide intra-familial clinical variability and variable disease penetrance were both confirmed, suggesting a role for modifying, still undetermined, factors, explaining the variable MEN1 tumorigenesis.

Screening of patients with multiple endocrine neoplasia type 1 (MEN-1): a critical analysis of its value

BACKGROUND

Screening of multiple endocrine neoplasia type 1 (MEN-1) patients is widely recommended because one-fifth succumb to malignant neoplasms. However, recommendations for screening modalities and intervals are based mostly on nonprospective data.

METHODS

Thirty-five of 48 MEN-1 patients were evaluated at least twice by an annual screening program in a single-center, prospective, nonrandomized study between 1997 and 2006. The screening program comprised anamnesis, clinical examination, imaging procedures, and extensive biochemical evaluations. Prospectively diagnosed lesions were evaluated separately from nonprospectively diagnosed lesions at first evaluation.

RESULTS

The median age of the patients was 45 years (range = 15-70) at initial assessment. They were followed for a median of 72 months (range = 24-108) by a median of 6 (range = 2-10) evaluations. The vast majority of lesions were nonprospectively diagnosed at initial evaluation: 13 of 17 patients had primary hyperparathyroidism (pHPT), 24 of 29 had pancreatic endocrine tumors (PETs), and 4 of 4 had carcinoids. Vice versa adrenal lesions were mostly prospectively detected (18/23). Malignancy was observed in 10 patients (28%) in the initial assessment and without symptoms in 5 patients (9 PETs, 3 carcinoids). Endoscopic ultrasound (EUS) of 29 patients detected 88 PETs which were followed for 157 patient years. The mean annual growing rate was 13.28 +/- 28.23 mm with respect to the baseline tumor diameter of 9 mm. In 35 patients the mean incidence of newly diagnosed PETs was 0.52/year. Adrenal lesions were invariably nonfunctional. A mean change in diameter of 6.7 +/- 23.44% was monitored and malignant transformation was absent.

CONCLUSIONS

Most lesions are detected at initial screening, particularly malignant tumors. Computed tomography of the abdomen and chest did not identify additional lesions. The interval between screenings could be extended to 3 years based on annually calculated growth rates and the incidence of MEN-1-associated lesions. The assessment of calcium, gastrin, and prolactin is sufficient for biochemical screening in MEN-1.