MEN 2A Families Research Articles

The Clinical Spectrum of Multiple Endocrine Neoplasia Type 2A with Cutaneous Lichen Amyloidosis in Ethnic Han Chinese

ABSTRACTThis study systematically reviewed previous literatures and analyzed the genotype–phenotype relationship between the multiple endocrine neoplasia type 2A (MEN 2A)-cutaneous lichen amyloidosis (CLA) and RET/OSMR/IL31RA mutations. RET/OSMR/IL31RA screening was performed on 8 RET-carriers from 3 independent Chinese MEN 2A families. Besides, 51 MEN 2A-CLA patients in 116 RET carriers from literatures were clustered and analyzed. Our results indicated that almost all MEN 2A-CLA patients exhibited CLA which was located in the scapular region and carried RET mutation at codon 634. Meanwhile, we firstly described MEN 2A-CLA here in Chinese Han patient with RET p.C634F mutation.

Founder Effect of the RETC611Y Mutation in Multiple Endocrine Neoplasia 2A in Denmark: A Nationwide Study.

Multiple endocrine neoplasia (MEN) 2A and 2B are caused by REarranged during Transfection (RET) germline mutations. In a recent nationwide study, an unusually high prevalence (33%) of families with the C611Y mutation was reported, and it was hypothesized that this might be due to a founder effect. The first nationwide study of haplotypes in MEN2A families was conducted, with the aim of investigating the relatedness and occurrence of de novo mutations among Danish families carrying similar mutations. The study included 21 apparently unrelated MEN2A families identified from a nationwide Danish RET cohort from 1994 to 2014. Twelve, two, two, three, and two families carried the C611Y, C618F, C618Y, C620R, and C634R mutations, respectively. Single nucleotide polymorphism chip data and identity by descent analysis were used to assess relatedness. A common founder mutation was found among all 12 C611Y families and between both C618Y families. No relatedness was identified in the remaining families. The data suggest that all families with the C611Y germline mutation in Denmark originate from a recent common ancestor, probably explaining the unusually high prevalence of this mutation. Additionally, the results indicate that the C611Y mutation rarely arises de novo, thus underlining the need for thorough multigenerational genetic work up in carriers of this mutation.

Three RET germ-line mutations in a family with multiple endocrine neoplasia type 2A syndrome

Multiple mutations in RET proto-oncogene are not common findings in patients with multiple endocrine neoplasia type 2A syndrome (MEN2A). Screening for RET mutation in MEN2A family members is usually limited by the known affected exon. However the second unrevealed mutation in RET proto-oncogene can coexist and modify the phenotype of MEN2 patients, including age of onset of medullary thyroid carcinoma, penetrance of pheochromocytoma etc. We here describe a family with MEN 2A syndrome with combination of three different germ-line RET mutations in its members (RET codon C634R, C634R+I852M, I852M+Y791F, Y791F). The earliest onset of medullary thyroid carcinoma was in a patient harboring the C634R+I852M double mutation at age 24 years. A 49-y.o.patient with C634R mutation has persistent medullary thyroid carcinoma after thyroidectomy at 35 years old. A carrier of Y791F mutation had no clinical evidence of disease at age of 28 years. In a child with compound I852M+Y791F mutation preventive thyroidectomy revealed C-cell hyperplasia at age of 4 years. The clinical significance of double RET mutation in the described family is not clear. Literature data of multiple germ-line RET mutations in patients with multiple endocrine neoplasia type 2A syndrome are presented.

Prophylactic thyroidectomy for asymptomatic 3-year-old boy with positive multiple endocrine neoplasia type 2A mutation (codon 634)

The multiple endocrine neoplasia type 2A (MEN 2A) syndrome, comprising medullary thyroid carcinoma (MTC), pheochromocytoma and primary hyperparathyroidism (PHPT) is most frequently caused by codon 634 activating mutations of the RET (rearranged during transfection) proto-oncogene on chromosome 10. For this codon-mutation carriers, earlier thyroidectomy (before the age of 5 years) would be advantageous in limiting the potential for the development of MTC as well as parathyroid adenomas. This is a case report of 3-year-old boy from the MEN 2A family (the boy's father and grandmother and paternal aunt) in which cysteine substitutes for phenylalanine at codon 634 in exon 11 of the RET proto-oncogene, who underwent thyroidectomy solely on the basis of genetic information. A boy had no thyromegaly, thyroidal irregularities or lymphadenopathy and no abnormality on the neck ultrasound examination. The pathology finding of thyroid gland was negative for MTC. Two years after total thyroidectomy, 5-year-old boy is healthy with permanent thyroxine replacement. His serum calcitonin level is < 2 pg/ml (normal < 13 pg/ml), has normal serum calcium and parathyroid hormone levels and negative urinary catecholamines. Long-term follow-up of this patient is required to determine whether very early thyroidectomy improves the long-term outcome of PHPT. Children with familial antecedents of MEN 2A should be genetically studied for the purpose of determining the risk of MTC and assessing the possibilities of making prophylactic thyroidectomy before the age of 5 years.

Fenotipo de la mutación C634Y del protooncogén RET en el MEN2A: a propósito de una familia

Background and objectives Genetic testing of RET proto-oncogen allows an early diagnosis of Multiple Endocrine Neoplasia syndrome type 2 and establish a correlation between genotype and clinical manifestations. The purpose of this study was to demonstrate the benefits of an early diagnosis with genetic testing followed by prompt surgery on the cure of MTC versus a later diagnosis with serum calcitonin. Patients and method Retrospective descriptive study of 8 members of a MEN 2A family by C634Y mutation. We performed serum calcitonin screening until 1999 and subsequently RET genetic testing was obtained. Carriers underwent total thyroidectomy and periodic determination of calcitonin, urinary metanephrines, calcium, phosphorus and neck and abdominal imaging techniques. Results Five patients were diagnosed by calcitonin familial screening and all of them have high calcitonin by now. Three patients were diagnosed by genetic testing (an adult and two children) and they are free of disease. Calcitonin was closely monitored in children and they underwent surgery when it started to raise, at 6 and 10 years old respectively, finding nodular C-cell hyperplasia in both. Of 8 carriers 3 developed pheochromocytomas, bilateral and asynchronous, one-half had normal urinary metanephrines and two of them were simultaneous with MTC. No patient had biochemical data suggesting hyperparathyroidism although in one patient multiple parathyroid adenomas were found at thyroidectomy. Conclusions RET genetic analysis has achieved an early diagnosis and treatment with no development of MTC in our patients, adjusting the time and type of surgery and allowing a genotype-phenotype correlation. It demonstrates how a genetic alteration is associated with a pathology that we can prevent and manage improving the prognosis of our patients.

RET mutation Tyr791Phe: the genetic cause of different diseases derived from neural crest

Activating germline RET mutations are presented in patients with familial medullary thyroid carcinoma (FMTC) and multiple endocrine neoplasia (MEN) types 2A and 2B, whereas inactivating germline mutations in patients with Hirschsprung's disease (HSCR). The aim of this study was to evaluate genotype-phenotype correlations of the frequently discussed Tyr791Phe mutation in exon 13 of the RET proto-oncogene. Screening of three groups of patients was performed (276 families with medullary thyroid carcinoma (MTC), 122 families with HSCR, and 29 patients with pheochromocytoma). We found this mutation in 3 families with apparently sporadic MTC, 3 families with FMTC/MEN2, 1 patient with pheochromocytoma, and 3 families with HSCR. All gene mutation carriers have a silent polymorphism Leu769Leu in exon 13. In three families second germline mutations were detected: Cys620Phe (exon 10) in MEN2A family, Met918Thr (exon 16) in MEN2B family, and Ser649Leu (exon 11) in HSCR patient. Detection of the Tyr791Phe mutation in MEN2/MTC and also in HSCR families leads to the question whether this mutation has a dual character (gain-of-function as well as loss-of-function). A rare case of malignant pheochromocytoma in a patient with the Tyr791Phe mutation is presented. This study shows various clinical characteristics of the frequently discussed Tyr791Phe mutation.

Application of genetic screening in families with hereditary medullary thyroid carcinoma.

In 34 families out of 35 with hereditary medullary thyroid cancer a mutation in the RET proto-ongene could be identified. In 84 family members gene carrier state could be proven, in 75 family members gene carrier state could be excluded. The majority of gene carriers (67 out of 84) were symptomatic while 17 gene carriers were diagnosed in a presymptomatic state. 9 of the 17 presymptomatic gene carriers had prophylactic thyroidectomy. On histological examination C-cell hyperplasia or multifocal microcarcinomas could be proven. In one of our families with familial MTC no germline mutation in the RET gene could be detected. In this family pentagastrintests and indirect genotyping are necessary. Four family members of MEN 2A families have had thyroidectomy on the basis of pentagastrin testing and now proved not to be gene carriers. The application of genetic testing in families with hereditary thyroid carcinoma has further improved management in these families - it is the first step in the evaluation of family members at risk.

Mutational Spectrum of Multiple Endocrine Neoplasia Type 2 and Sporadic Medullary Thyroid Carcinoma in Taiwan

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant cancer predisposition syndrome, and > 95% of MEN 2 patients carry rearranged during transfection (RET) protooncogene mutants. We aimed to elucidate the genotype and phenotype relationship of RET proto-oncogene mutations in Taiwanese subjects with medullary thyroid cancer (MTC). We genotyped the MEN-2-associated germ-line mutations by PCR-based sequencing of the RET gene. DNA was extracted from a total of 69 members from eight unrelated families with individuals affected by MTC, and from seven sporadic cases of MTC. RET mutations were found in four MEN 2A families, all at codon 634 (one with C>R, two with C>F, and one with C>W). One MEN 2A patient carried a de novo mutation at codon 634 (C>R). In two families of MEN 2B, all carried the mutation at codon 918 (M>T). These two cases of MEN 2B were all de novo mutations. One family of familial MTC or unclassified MEN 2 carried the codon 620 (C>F) mutation. Among the seven sporadic cases of MTC, none was found to carry any mutation in hotspot exons. Only two non-synonymous variants (T278N/exon 4 and D489N/exon 7) were found in two cases. However, these two variants were not uncommon in our elderly population. We found that all eight MTC patients with a family history or with the other phenotypes of MEN 2 had RET mutations, whereas no significant RET mutation was found in seven patients with isolated MTC without family history and other endocrine diseases. Molecular scanning of the RET gene in MEN 2 and MTC in Taiwanese patients probably should be limited to exons 10, 11 and 16, initially to be cost-effective.

Pheochromocytoma in MEN 2A Syndrome. Study of 54 Patients

Pheochromocytoma occurs in nearly 50% of MEN 2A (multiple endocrine neoplasia, type 2A) cases. Many issues related to this tumor are still the subject of debate: the diagnostic management in patients who have had positive genetic study results (RET mutation), variations related to mutation, the best surgical option, and the real relapse rate during long-term follow-up. The aim of this study is to present our experience with this unusual disease, looking for answers to some of these questions. Of 169 patients belonging to 19 MEN 2A families, 54 (32%) presented with pheochromocytoma. The following variables have been studied: (1) clinical and diagnostic data [age, mutation, clinical features, results of catecholamines and catabolites in a 24-h urine sample, computerized tomography (CT) scan and iodine-131 meta-iodobenzylguanidine (MIBG) scintigraphy results, and the means of diagnostic, clinical, or genetic screening]; (2) surgical treatment; and (3) follow-up and recurrence. The mean follow-up time was 92.5 months (range: 12-120 months). The mean age of the 54 patients was 37.9 years (range: 14-71 years); 33 were women. Most (96.3%) mutations were found in exon 11. The most frequent mutations were Cys634Tyr (in 33 cases [61.1%]) and Cys634Arg (in 14 [25.9%]). The diagnosis of pheocromocytoma was made after the diagnosis of MTC in 26 cases (48.2%), simultaneously in 21 (38.9%), and prior in the 7 remaining cases (12.9%). At the time of diagnosis 28 patients (51.8%) were asymptomatic and 26 (48.2%) had clinical features related to pheochromocytoma. In 6 patients (11.1%), the values of catecholamines and catabolites in urine were normal. In the cases with high values, the most useful isolated determination was that of metanephrines (82%), followed by adrenaline (76%). The CT scan did not provide a correct diagnosis in 6 patients with bilateral lesions, and one patient with a bilateral tumor was not diagnosed by MIBG. The combination of CT scan and MIBG diagnosed 100% of cases. The pheochromocytoma was bilateral in 27 cases, with a total number of 81 pathological glands detected. A laparascopic approach was used in 30 cases and a laparotomy in 24. The mean tumor size was 4.5 cm (range: 1-18 cm). Five patients with unilateral resection relapsed (18.5%), and the mean relapse time was 43.2 months (range: 12-120 months). There was a greater frequency of pheochromocytoma in those subjects who had the Cys634Arg mutation (p < 0.03). In addition, the Cys634Arg mutation is more frequent in bilateral cases. There are no prognostic factors for recurrence. Pheochromocytoma in MEN 2A is related to the type of mutation, which can be early onset and is frequently asymptomatic. Its diagnosis requires catecholamines determinations as well as a CT scan. Correct diagnosis of bilaterality is established by CT and MIBG. Laparoscopic adrenalectomy is the treatment of choice.

C634R mutation of the protooncongene RET and molecular diagnosis in multiple endocrine neoplasia type 2 in a large Moroccan family

Multiple endocrine neoplasia (MEN) 2A is an inherited disease characterized by the development of medullary thyroid carcinoma (MTC), pheochromocytoma and/or hyperparathyroïdism. It has been shown to be associated with germline mutations in the RET proto-oncogene. Direct DNA testing, therefore allows the identification of subjects with asymptomatic MEN 2A who can be offered prophylactic thyroidectomy and biochemical screening as preventive measures. DNA analysis of RET exon 8, 10, 13, 14, 15 and 16 was performed by direct sequencing of PCR product on automated sequencer and or PCR-digestion. In this report, we describe a MEN2A family witch initially seemed a sporadic case of MTC. We first characterized the C634R RET mutation in the index and then we identified 3 carriers who developed the disease and 3 young carriers who were apparently asymptomatic. A genetic counselling and the management of the carriers were proposed. This study confirmed that genetic testing ; in order to detect gene carriers is technically possible in Morocco. This will contribute to the definition of a national policy of this cancer control.

RET proto-oncogene testing in infants presenting with Hirschsprung disease identifies 2 new multiple endocrine neoplasia 2A kindreds

Multiple endocrine neoplasia 2A (MEN 2A) is a genetic syndrome manifesting as medullary thyroid carcinoma (MTC), hyperparathyroidism, and pheochromocytoma. Multiple endocrine neoplasia 2A results from mutations in the RET proto-oncogene. Hirschsprung disease (HSCR) is a rare manifestation of MEN 2A and has been described in known MEN 2A families. Here we describe 2 MEN 2A families that were only identified after the diagnosis of HSCR. Kindred 1: A boy presented in infancy with HSCR. Genetic screening revealed a C609Y mutation, which is consistent with MEN 2A. Evaluation of his sister, father, and grandmother revealed the same mutation. All 3 had thyroidectomies demonstrating C-cell hyperplasia. The grandmother had a microscopic focus of MTC. Kindred 2: An infant boy and his sister were diagnosed with HSCR as neonates. Genetic testing demonstrated a C620R gene mutation consistent with MEN 2A. Total thyroidectomies revealed metastatic MTC in the father and C-cell hyperplasia in both children. Hirschsprung disease can be the initial presentation of MEN 2A. We strongly recommend that genetic screening be performed in patients presenting with HSCR, looking for the known RET mutations associated with MEN 2A. If a mutation consistent with MEN 2A is detected, genetic screening of all first-degree relatives in the kindred is recommended.

A Family of Multiple Endocrine Neoplasia Type 2A (MEN 2A) with Cys630Tyr RET Germline Mutation: Report of a Case

Since the majority of multiple endocrine neoplasia type 2A (MEN 2A) patients have missense mutations at codon 634 and those with the Cys630 RET genotype mutations are extremely rare, limited clinical information is available about this rare type. We report here three members of one Japanese MEN 2A family with the Cys630Tyr genotype. A 67-year-old woman presented a firm thyroid nodule, and preoperative examination revealed medullary thyroid carcinoma with primary hyperparthyoidism and no pheochromocytoma. At surgery, bilateral medullary thyroid carcinomas and parathyroid adenoma were found. No lymph node metastasis was identified. Computed tomography scans and laboratory examination of blood have shown no evidence of tumor recurrence and no abnormality of parathyroid function during the 4 years after surgery. A 40-year-old man, the proband's son, was shown to have the same RET mutation, underwent total thyroidectomy prophylactically, and only microscopic foci of medullary thyroid carcinoma were found. A 10-year-old boy, the proband's grandson also having the same RET mutation, showed normal basal serum calcitonin level and has been followed up conservatively. To our knowledge, 18 patients of 6 families with the Cys630 mutations have been reported so far. This is only the second reported case with primary hyperparathyroidism. RET 630 mutations might be associated with lower penetrance of primary hyperparthyoidism and pheochromocytoma.

Experience of prophylactic thyroidectomy in multiple endocrine neoplasia type 2A kindreds with RET codon 804 mutations

Genetic screening in multiple endocrine neoplasia type 2 (MEN 2) has led to specific management guidelines based on genotype-phenotype analysis. However, there is controversy regarding the appropriate age for prophylactic thyroidectomy in families with mutations in codon 804 in exon 14 of the RET proto-oncogene, where medullary thyroid cancer (MTC) may not develop until adulthood. We prospectively studied two MEN 2A families, one with the V804L and the other with the V804M RET mutation, to report our experience of genetic and biochemical screening and prophylactic thyroidectomy. Family 1 is one of the largest MEN 2A families in the literature, where 22 prophylactic thyroidectomies have been performed. C-cell hyperplasia (CCH) was found in 23 out of 25 thyroidectomy specimens from family members of ages 5 years and upwards. MTC was found in 10 out of 18 adults of age 25 years upwards, including the family 2 proband, who was found to have MTC with lymph node metastases at age 28. Phaeochromocytoma was only observed in one patient, but six cases of histologically confirmed hyperparathyroidism were seen in family 1. We suggest that prophylactic thyroidectomy should not be delayed until adulthood in MEN 2A families carrying codon 804 RET mutations, but should be performed when there is CCH, before the development of MTC, as close as possible to age 6 years, which is the age of the youngest reported case of MTC in '804' families.

Screening of six risk exons of the RET proto-oncogene in families with medullary thyroid carcinoma in the Czech Republic

Medullary thyroid carcinoma (MTC) occurs as a sporadic form (75%) or as an autosomal dominant inherited familial disorder (25%) called familial MTC (FMTC) or as multiple endocrine neoplasia type 2 (MEN2) syndromes. Germ-line mutations in the rearranged during transfection (RET) proto-oncogene in exons 10, 11, 13, 14, 15 and 16 are known to be a cause of most of the familial forms. In this paper we report molecular genetic testing of 106 families with MTC (358 tested persons) from the Czech Republic in which we directly sequenced these six exons of the RET proto-oncogene. We detected germ-line mutations in 100% of MEN2B families (4/4 families), 90% of MEN2A families (9/10), 40% of FMTC families (4/10) and 7% of apparently sporadic MTC (6/82). Eleven different germ-line mutations were revealed. MEN2B was associated with mutation Met918 Thr in exon 16. In one MEN2B family beside this mutation the Tyr791 Phe was also found, which has not yet been reported. MEN2A was restricted to different mutations in exon 11 (codon 634). In FMTC and 'sporadic' MTC families the mutations in exons 10, 11, 13 and 14 were detected. The genotype/phenotype correlations are given. Genetic testing revealed germ-line mutations in 23 index patients, 24 family members and excluded them in 53 relatives.

RET Oncogene Mutations in Medullary Thyroid Carcinoma in Mexican Families

Background Different RET oncogene mutations have been found to be associated with inherited medullary thyroid carcinoma (MTC) in the context of three different syndromes including multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B) and familial medullary thyroid carcinoma (FMTC). These mutations have been recorded in different populations, but to date there is no corresponding study in Mexican families. Our purpose was identification of RET mutations in Mexican families with inherited or sporadic MTC (SMTC) and search for RET protein expression as prognostic marker in MTC tumors. Methods Nine unrelated families with MTC corresponding either to two MEN 2A, three MEN 2B, or four SMTC were studied. Screening of exons 10, 11, and 13–16 of RET oncogene in DNA from circulating lymphocytes and tumor samples were analyzed. Immuno- staining for RET was performed in the corresponding tumor. Results Germline 918 ATG→ACG RET mutation was present in three unrelated MEN 2B individuals and corresponding somatic mutation in one individual with SMTC; 634 TGC→TTC RET mutation was detected in two related patients in an MEN 2A family and the 634 TGC→TAC RET mutation was detected in 12 related individuals from a second MEN 2A family. RET protein expression was detected in all MTC tumors showing different staining intensity. Conclusions RET mutations found in Mexican patients with MTC are similar to those previously reported in several MTC families worldwide. This indicates that RET mutations are highly conserved and that MTC etiology does not depend to a great extent on environmental factors or ethnic differences. Detection of RET protein in MTC tissue sections is not useful as prognostic marker.

MEN 2A families: from hot spots to hot regions.

The aim of this study was to look for common ancestors among MEN 2A Portuguese families presenting with the same germ-line mutation of the RET proto-oncogene. To address this question from a genetic point of view, we performed haplotype analysis in six out of nine, apparently separate, MEN 2A families using four polymorphic markers. Three families carrying the C634R mutation and presenting the same phenotype shared the same haplotype surrounding the MEN 2A mutation. Moreover, these families were originally from the same geographic region although settled at different places along the country. Altogether, data suggested a common ancestral MEN 2A chromosome for three families. Since MEN 2A is a rare inherited cancer syndrome, identification of common ancestors may draw attention for specific geographic regions from where other affected families may arise at a higher chance and, therefore, termed 'hot regions'.

Analysis of Mutations of the RET Proto-oncogene in Patients with Medullary Thyroid Carcinoma

The spectrum of mutations of the RET proto-oncogene was analyzed in Russian patients with inherited or sporadic medullary thyroid carcinoma (MTC). Four RET exons (11, 13, 15, and 16) were subjected to molecular analysis, and mutations were revealed and identified in 47.4% (9/19) patients with sporadic MTC. In total, six different mutations (including three new ones) were observed. The most common mutation affected codon 918 to cause substitution of methionine with threonine and accounted for 31.6% alleles. Analysis of exons 11 and 16 revealed four types of mutations in patients with inherited multiple endocrine neoplasia type 2 (MEN 2). Mutations were found in each patient. Thyroidectomy was performed in four asymptomatic carriers of RET mutations from three MEN 2A families (in two families, affected relatives had bilateral pheochromocytoma). In two patients, analysis of the surgery material revealed MTC microfoci in both lobes of the thyroid gland. The results provide the ground for constructing a bank of genetic information on Russian MTC patients with the clinically verified diagnosis.

Occurrence of Pheochromocytoma in a MEN2A Family with Codon 609 Mutation of the RET Protooncogene

Occurrence of Pheochromocytoma in a MEN2A Family with Codon 609 Mutation of the RET Protooncogene

A PCR-mutagenesis strategy for rapid detection of mutations in codon 634 of the ret proto-oncogene related to MEN 2A.

BackgroundMultiple endocrine neoplasias type 2A (MEN 2A) is a dominantly inherited cancer syndrome. Missence mutations in the codon encoding cysteine 634 of the ret proto-oncogene have been found in 85% of the MEN 2A families. The main tumour type always present in MEN 2A is medullar thyroid carcinoma (MTC). Only 25% of all MTC are hereditary, and generally they are identified by a careful family history. However, some familial MTCs are not easily detected by this means and underdiagnosis of MEN 2A is suspected.MethodsDNA samples from MEN 2A patients were amplified by PCR. The products were incubated with the restriction enzyme Bst ApI or Bgl I.The samples were loaded in non-denaturing 10% Polyacrilamyde Gel and run at 120 volts for 40 min. The gels were stained with 10 μg/ml ethidium bromide, and the bands were visualized under a UV lamp.ResultsWe developed a PCR-mutagenic method to check the integrity of the three bases of the cysteine 634 codon.ConclusionThe method can be used to detect inherited mutations in MTC patients without a clear family history. The method is relatively simple to use as a routine test in these patients to decrease the underdiagnosis of MEN 2A. In addition, the assay can be used to screen affected families with any mutation in cysteine 634.

Genetic analysis of RET, GFR alpha 1 and GDNF genes in Spanish families with multiple endocrine neoplasia type 2A.

Multiple endocrine neoplasia type 2A (MEN 2A) is associated with specific germline missense mutations in the RET proto-oncogene. This locus encodes a receptor tyrosine kinase whose activation requires the formation of a multimeric receptor complex including GDNF as a ligand and GFR alpha 1 as a coreceptor. In order to explore the role of RET, GFR alpha 1 and GDNF genes in the variation of phenotypes observed in MEN2A families, we analysed germline mutations of these genes in 4 unrelated Spanish MEN2A families (23 cases studied). We found 2 novel variants corresponding to a single change in position + 47 (intron 12) of RET and position +22 (intron 7) of GFR alpha 1. Furthermore, we observed strong co-segregation between 2 polymorphisms of RET [G691S (exon 11) and S904S (TCC-TCG, exon 15) (100%, Fisher's exact test, p< 0.001)]. More interestingly, we found that these polymorphisms occurred at a significantly high frequency in patients with age at onset < 20 years old (Kruskal-Wallis's and Fisher's exact test, p = 0.007). These findings suggest that the G691S and S904S variants of RET may somehow play a role on the age of onset of MEN 2A.