Unusual presentation of multiple endocrine neoplasia type 1 in a young woman with a novel mutation of the MEN1 gene

True MEN1 or phenocopy? Evidence for geno-phenotypic correlations in MEN1 syndrome

PURPOSE

Multiple endocrine neoplasia type 1 is a rare tumor syndrome caused by germline mutations of MEN1 gene. Phenotype varies widely, and no definitive correlation with the genotype has been observed. Mutation-negative patients with MEN1-associated tumors represent phenocopies. By comparing mutation-positive and mutation-negative patients, we aimed to identify phenotype features predictive for a positive genetic test and to evaluate the role of MEN1 mutations in phenotype modulation.

METHODS

Mutation screeening of MEN1 gene by Sanger sequencing and assessment of clinical data of 189 consecutively enrolled probands and relatives were performed at our national and European Reference Center. Multiple ligation probe amplification analysis of MEN1 gene and Sanger sequencing of CDKN1B were carried out in clinically suspicious but MEN1-negative cases.

RESULTS

Twenty-seven probands and twenty family members carried MEN1 mutations. Five mutations have not been described earlier. Pronouncedly high number of phenocopies (>70%) was observed. Clinical suspicion of MEN1 syndrome emerged at significantly earlier age in MEN1-positive compared to MEN1-negative probands. Gastroenteropancreatic neuroendocrine tumors developed significantly earlier and more frequently in carriers compared to non-carriers. Probands with high-impact (frameshift, nonsense, large deletions) mutations, predicted to affect menin function significantly, developed GEP-NETs more frequently compared to low-impact (inframe and missense) mutation carriers.

CONCLUSIONS

MEN1 phenocopy is common and represents a significant confounder for the genetic testing. GEP-NET under 30 years best predicted a MEN1 mutation. The present study thus confirmed a previous proposal and suggested that GEP-NET under 30 years should be considered as a part of the indication criteria for MEN1 mutational analysis.

MEN1 gene mutations in Hungarian patients with multiple endocrine neoplasia type 1

OBJECTIVE

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant hereditary disorder associated with mutations of the MEN1 gene. MEN1 may present as a familial or a sporadic disorder, with multiple endocrine tumours including parathyroid adenomas or hyperplasias, and pancreatic endocrine and pituitary gland tumours. The aim of this study was to examine the prevalence and spectrum of MEN1 gene mutations in Hungarian patients with familial and sporadic MEN1 and in those with a MEN1-related state.

DESIGN

Mutation analysis, using temporal temperature gradient gel electrophoresis and direct sequencing of all coding exons and the corresponding exon-intron boundaries of the MEN1 gene, was performed.

PATIENTS AND MEASUREMENTS

Peripheral blood DNA was obtained from 32 patients (19 index patients with familial or sporadic MEN1 and 13 index patients with familial or sporadic MEN1-related state). First degree relatives were also studied.

RESULTS

Ten different MEN1 gene mutations were identified in 10 index patients, including four novel mutations (A91V, G28A and E26X all in exon 2, and L301R in exon 6). All but one mutation occurred in index patients with familial or sporadic MEN1; the prevalence of mutation was considerably higher in index patients with familial MEN1 (6/6 patients, 100%) than in those with sporadic MEN1 (3/13 patients, 23%). Of the 13 index patients with a MEN1-related state, only one patient with recurrent isolated primary hyperparathyroidism had a MEN1 gene mutation. Family screening indicated mutations in six symptomatic and in one asymptomatic first degree relative.

CONCLUSION

These results confirm previous reports on the high prevalence of novel MEN1 gene mutations among patients with MEN1, and support the questionable efficacy of mutation screening in patients with sporadic MEN1-related states.

Contribution of genetic analysis in screening for MEN1 among patients with sporadic disease and one or more typical manifestation

Multiple Endocrine Neoplasia type 1 (MEN1) is an autosomal dominant hereditary syndrome (OMIM 131100) due to MEN1 gene mutations, predisposing to the development of hyperplasic and tumoral lesions of neuroendocrine tissues. Since the identification of the gene in 1997, more than 400 different mutations of MEN1 have been registered. Genotypic analysis of MEN1 remains fastidious and must be reserved to targeted situations. If the lesions appear in a familial assessed context, there is a strong argument to search for MEN1 mutation. This is not the case in a sporadic context. With experience acquired in our laboratory, we evaluated the frequency of MEN1 mutations in patients with sporadic presentations. Our aim was to better define criteria for MEN1 genotypic analysis. One hundred and twenty four blood samples from unrelated patients, who gave their written informed consent, were analyzed. These patients exhibited 1 to 4 manifestations of MEN1 without any familial context. After DNA extraction, the analysis was undertaken by PCR-sequencing of all the MEN1 coding exons and exon/intron boundaries or by PCR of the pre-screened fragments alone, a technique made possible by indirect screening mutation methods. Mutations were identified by comparing the sequences to the reference MEN1 sequence available from GENBANK (U93237.1). Mutations were identified in 19 patients, with variable prevalence according to clinical manifestations: 100% for patients with 4 manifestations, 45.5% for patients with 3 manifestations, 19% for patients with 2 manifestations and 2% for patients with only one manifestation. Mutations were: 11 point variations (58%), including 2 splicing sites and 8 frameshift mutations (42%) including 5 deletions, 2 insertions and 1 insertion/deletion; one mutation was identified twice. We showed a relationship between clinical presentation and MEN1 mutation identification, especially with the number of clinical manifestations but also with the type of manifestation. Pancreatic manifestations were significantly linked with probability of mutation. In a sporadic context with at least two established manifestations of MEN1, the overall probability of identifying a mutation was 26%, warranting MEN1 genotypic analysis.