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PubMed1998

Germline RET proto-oncogene mutations in two Taiwanese families with multiple endocrine neoplasia type 2A.

To elucidate the germline RET proto-oncogene mutations in Taiwanese families with multiple endocrine neoplasia type 2A (MEN 2A), we extracted DNA from peripheral blood leukocytes of 28 members of two families with MEN 2A. Oligonucleotide primers for exons 10 and 11 were used to analyze the nucleotide sequence of codons 609, 611, 618, and 620 of exon 10, and codon 634 of exon 11 of the RET proto-oncogene. Two fragments of genomic DNA were amplified by polymerase chain reaction (PCR). The amplified PCR products were separated and purified from primers and free nucleotides in agarose gels, and the expected 187-bp and 234-bp bands were cut from the gels and sequenced. Thirteen family members in the two MEN 2A kindreds had mutations in codon 634 of exon 11. In kindred 1 (15 members available for this study), a heterozygous codon 634 mutation in nine members and a homozygous codon 634 mutation in one member led to the substitution of Phe (TTC) for Cys (TGC). Three members of kindred 2 (13 members available for this study) had a heterozygous base pair change in codon 634, which led to the substitution of Arg (CGC) for Cys (TGC). In this study, we found two mutation events occurring in two MEN 2A kindreds and also discovered a homozygous point mutation in one woman that led to heterozygous mutations in all of her children.

Drosophila Proteins↗

PubMed1997

False-positive results of basal and pentagastrin-stimulated calcitonin in non-gene carriers of multiple endocrine neoplasia type 2A.

Direct DNA analysis permits accurate identification of gene carriers in kindred members with multiple endocrine neoplasia type 2A (MEN 2A). The aim of this study was to assess the specificity of basal and pentagastrin stimulated calcitonin levels in 3 family members with MEN 2A. For this purpose 53 members of 3 consecutive families with MEN 2A were evaluated in a university medical center. Serum calcitonin, basal and stimulated, was determined by a commercial RIA. RET protooncogene analysis was carried out by automatic DNA sequencing and adequate digestion of PCR amplified products for exons 10 and 11. Two distinct mutations in the RET protooncogene were identified. A T-->A transition at position 1783 (codon 618) in exon 10 was detected in one family, and a G-->A replacement at position 1832 (codon 634) in exon 11 in the others. In non-gene carriers we obtained 6.6% of false-positive results for basal calcitonin and 15.4% for the pentagastrin provocative test. We conclude that the specificity of basal and pentagastrin-stimulated calcitonin is rather limited and RET protooncogene analysis must be the first line screening procedure in order to identify gene carriers.

Adolescent↗

PubMed2002

A novel Val648Ile substitution in RET protooncogene observed in a Cys634Arg multiple endocrine neoplasia type 2A kindred presenting with an adrenocorticotropin-producing pheochromocytoma.

Multiple endocrine neoplasia type 2 (MEN 2) comprises a heterogeneous group of neoplasic disorders that most commonly have a single missense substitution of the RET protooncogene (RET) involving exons 10 and 11. It was previously reported a MEN 2A kindred in which the father presented with a rare phenotype consisting of bilateral ACTH-producing pheochromocytoma and medullary thyroid carcinoma. We recently performed mutational analysis of the father and his 4 children using a denaturing gradient gel electrophoresis approach and PCR-amplified genomic DNA, followed by direct sequencing or restriction fragment length polymorphism testing. All 4 children showed a RET sequence variation. The common exon 11 Cys(634)Arg RET mutation was present in 2 of the 4 children who had undergone thyroidectomy for C cell disease. The remaining 2 children, who did not harbor the Cys(634)Arg mutation and are negative for C cell and adrenal disease, carry a previously unreported Val(648)Ile missense change in RET exon 11. This novel substitution was not found in the unaffected mother or in 200 control alleles. Both RET variants were present in the father affected with MEN 2A and the unusual ACTH-producing pheochromocytoma. We speculate that the double RET mutation may have modified and contributed to the rare MEN 2A phenotype in the father.

Adrenal Gland Neoplasms↗

PubMed1990

The natural history of multiple endocrine neoplasia type 2A--a clinical analysis.

The records of 18 patients with multiple endocrine neoplasia (MEN) type 2A in a family consisting of 87 members in 5 generations, were reviewed with respect to age at onset and length of survival in a study of the natural history of this syndrome. Of these 18 patients, 8 were alive following surgical treatment, while 10 had died without treatment. The clinical onset of medullary thyroid carcinoma was noticed as a nodule in the neck at between 17 and 34 years of age (mean 24 years); the onset of pheochromocytoma was characterized by palpitation, hypertensive attacks or recurrent headache at between 17 and 42 years of age (mean 27 years); and death occurred in 10 patients at between 23 and 67 years of age (mean 40.6 years). This information on the age at onset of individual clinical manifestations, and on the length of survival of gene carriers, may be useful for clinicians who are asked to assess the risk of the development of this syndrome in a genetically predisposed asymptomatic individual, because screening tests are often refused by members of Japanese families with MEN type 2A.

Adolescent↗

PubMed1996

A mutation in the RET proto-oncogene in Hirschsprung's disease affects the tyrosine kinase activity associated with multiple endocrine neoplasia type 2A and 2B.

We demonstrate that a Hirschsprung (HSCR) mutation in the tyrosine kinase domain of the RET proto-oncogene abolishes in cis the tyrosine-phosphorylation associated with the activating mutation in multiple endocrine neoplasia type 2A (MEN2A) in transiently transfected Cos cells. Yet the double mutant RET2AHS retains the ability to form stable dimers, thus dissociating the dimerization from the phosphorylation potential. Co-transfection experiments with single and double mutants carrying plasmids RET2A and RET2AHS in different ratios drastically reduced the phosphorylation levels of the RET2A protein, suggesting a dominant-negative effect of the HSCR mutation. Also, the phosphorylation associated with the multiple endocrine neoplasia type 2B (MEN2B) allele was affected in experiments with single and double mutants carrying plasmids co-transfected under the same conditions. Finally, analysis of the enzymic activity of MEN2A and MEN2B tumours confirmed the relative levels of tyrosine phosphorylation observed in Cos cells, indicating that this condition, in vivo, may account for the RET transforming potential.

Animals↗

PubMed2005

Resection of phaeochromocytoma extending into the right atrium in a patient with multiple endocrine neoplasia type 2A.

We report the first case of successful surgical resection of a malignant phaeochromocytoma with tumour extension into vena cava and right atrium in a patient with multiple endocrine neoplasia type 2A. A 21-year-old woman with genetic confirmation of multiple endocrine neoplasia type 2A syndrome was diagnosed with a very rare case of malignant phaeochromocytoma with tumour thrombus extension into vena cava and right atrium causing Budd-Chiari syndrome. It posed a challenge to the surgeons with regard to complete tumour resection and vascular control. Reviewing the limited literature, surgical resection by means of cardiopulmonary bypass with hypothermic circulatory arrest has been reported with success in phaeochromocytoma with advance vascular involvement. Adopting this approach, adrenalectomy with complete thrombus excision by inferior vena cava exploration and right atriotomy were performed successfully by a multidisciplinary team.

Adrenal Gland Neoplasms↗

PubMed1989

Cutaneous lichen amyloidosis associated with multiple endocrine neoplasia type 2A.

We have previously described a kindred with hereditary medullary thyroid carcinoma and pheochromocytoma (multiple endocrine neoplasia type 2A [MEN 2A]) with localized pruritic cutaneous manifestations present only in affected members. Although the initial skin biopsies reported did not show amyloidosis, subsequent skin biopsy results reported here have demonstrated amyloid which stained for keratin but not for calcitonin and established that this family represents an association of a rare autosomal dominant form of lichen amyloidosis with MEN 2A.

Adrenal Gland Neoplasms↗

PubMed1998

Germ line mutation analysis in families with multiple endocrine neoplasia type 2A or familial medullary thyroid carcinoma.

The RET proto-oncogene has been identified as the multiple endocrine neoplasia type 2 disease gene. An association between specific RET mutation and disease phenotype has been reported. We present the phenotype-genotype of 12 Greek families with multiple endocrine neoplasia type 2A (MEN 2A) or familial medullary thyroid carcinoma (FMTC). Seventy members were studied and DNA analysis for RET mutations was performed in fifty-eight of them. Exons 10, 11, 13, 14 and 16 of the RET proto-oncogene were analyzed by single strand conformation polymorphism analysis, direct DNA sequencing and/or restriction enzyme analysis. No mutations of the RET proto-oncogene were identified in 1 of 9 families with MEN 2A and in the 3 families with FMTC. In 7 MEN 2A families, the mutation was demonstrated in codon 634 and in 1 family it was demonstrated in codon 620. There was a low frequency, about 8%, of hyperparathyroidism associated with MEN 2A. The specific causative mutations for pararthyroid disease were C634R or C634Y. Among the MEN 2A individuals there was one case with de novo C634R mutation and one case, C634Y, with cutaneous lichen amyloidosis which predated by 24 years the diagnosis of MEN 2A. In 2 children who were MEN 2A gene carriers, microscopic medullary thyroid carcinomas were found. These data show a low frequency of hyperparathyroidism in our cases and provide further evidence that individuals with C634R as well as with C634Y mutations of the RET proto-oncogene could be at risk for parathyroid disease. Cutaneous lichen amyloidosis could be an early feature of MEN 2A. Additionally, direct DNA testing provided an opportunity to resect medullary thyroid carcinoma at an early stage.

Adolescent↗

PubMedDate not supplied

Prominent corneal nerves in patients with multiple endocrine neoplasia type 2A: diagnostic implications.

We examined corneal nerves of 22 patients from 10 families with multiple endocrine neoplasia type 2A (MEN-2A). According to the findings in slit-lamp biomicroscopic examination and photographic documentation, the increased visibility of corneal nerves were classified into 5 grades (Grade 0 = invisible to Grade 4 = as thick as in MEN-2B). All eyes of normal subjects, 19 of 20 eyes of patients with anterior keratoconus, and 11 of 12 eyes of patients with non-hereditary medullary thyroid carcinoma (MTC) were either grade 0 or 1, and the remaining 2 eyes were evaluated as grade 2. Of the 44 eyes of MEN-2A patients, 5 (11.4%) eyes were grade 0, 11 (25%) eyes were grade 1, 19 (43.2%) eyes were grade 2, 8 (18.2%) eyes were grade 3, and 1 (2.3%) eye was grade 4. Thus, more than 60% of eyes of MEN-2A patients showed pathologically thickened corneal nerves of varying degree (grade 2 or higher). There was no definite relationship between the grade of corneal nerve thickening and the patient's age or presence of pheochromocytoma. Differences in the grade of corneal nerve thickening were observed among affected members belonging to the same MEN-2A family, but unaffected members of the family never showed prominent corneal nerves of grade 2 or higher. Our findings suggest that MTC patients with thickened corneal nerves might actually be MEN-2A patients and should be carefully followed for other components of this syndrome.

Adolescent↗

PubMed1994

Predictive DNA testing and prophylactic thyroidectomy in patients at risk for multiple endocrine neoplasia type 2A.

BACKGROUND: Missense germ-line mutations in the RET protooncogene are associated with multiple endocrine neoplasia type 2A (MEN 2A). Detection of these mutant alleles in kindred members predicts disease inheritance and provides the basis for preventative thyroidectomy. METHODS: A polymerase chain reaction (PCR)-based genetic test for the 19 known RET mutations was designed to study 132 members of 7 kindreds with MEN 2A. Haplotypes also were constructed using genetic markers flanking the MEN 2A locus. Plasma calcitonin (CT) concentrations were determined before and after provocative testing. RESULTS: Direct DNA testing and haplotype analysis showed that 21 of 58 kindred members at risk for disease had inherited a mutation in the RET protooncogene associated with MEN 2A. Plasma CT concentrations were elevated in 9 of the 21 family members, but were normal in 12. After genetic counseling, 13 of the 21 kindred members (6 with normal and seven with elevated plasma CT levels), consented to immediate thyroidectomy. In each patient, the resected thyroid gland showed C-cell hyperplasia with or without medullary thyroid carcinoma. There were no metastases to regional lymph nodes, and postoperative stimulated plasma CT levels were normal. CONCLUSION: The PCR-based direct DNA test for RET mutations is accurate, rapid, and reproducible. For all 132 individuals evaluated, the results of direct DNA analysis were consistent with haplotype studies. The direct test for mutations in the RET protooncogene is the preferred method for screening MEN 2A kindreds. In family members who have inherited a RET mutation, total thyroidectomy is indicated, regardless of the plasma CT values.

Adolescent↗

PubMed1998

Seventeen-year-long follow-up of a family affected by type 2A multiple endocrine neoplasia (MEN 2A).

This paper reports the results of a 17-year-long follow-up covering 17 members of a family affected by multiple endocrine neoplasia (MEN) type 2A, first diagnosed in 1980. This family is enrolled in our screening program. The thyroid, parathyroid and adrenal glands of the family members were investigated using the most sophisticated and sensitive techniques which have become available during this period, and their DNA was genetically tested for detecting RET mutations. Thanks to the combination of these two approaches it was possible to confirm the diagnosis in the members concerned from the genetic point of view, and to achieve an early diagnosis in the young members of the last generation before the clinical onset of the disease. The detection of a RET mutation also prompted a prophylactic thyroidectomy in a four year-old boy, in a pre-tumoral stage of the disease. Lastly, evidence is provided that genetic analysis of the DNA of the chorionic villi can be carried out as a prenatal test during routine amniocentesis.

Adolescent↗

PubMed2001

[From gene to disease; from the RET gene to multiple endocrine neoplasia types 2A and 2B, sporadic and familial medullary thyroid carcinoma, Hirschsprung disease and papillary thyroid carcinoma].

The RET gene encodes a receptor tyrosine kinase involved in normal and neoplastic development of neural crest cell lineages. Activating RET mutations are present in patients with multiple endocrine neoplasia types 2A and 2B (MEN2A, 2B) and in familial medullary thyroid carcinoma (FMTC) patients, whereas inactivating RET mutations are found in patients with Hirschsprung (HSCR) disease. In particular for MEN2A and FMTC, the clinical management largely depends on the specific mutation found.

Carcinoma, Medullary↗

PubMed1990

Application of linked DNA markers to screening families with multiple endocrine neoplasia type 2A.

There now exists a set of tightly linked markers to the gene causing multiple endocrine neoplasia type 2A. In this report we discuss the use of these markers for early and accurate prediction of gene carrier status in three different families. Factors that influence the probability of obtaining useful information with DNA markers are available family size, in particular the number of available affected individuals, and the extent of clinical and biochemical screening in the family. At present, DNA analysis has about a 3% risk of misdiagnosis; this risk is even lower if it is used in conjunction with the pentagastrin stimulation test for C-cell hyperplasia. With the combined tests, an individual at age 20 years may be scored as carrier or not with an estimated accuracy of 99%.

Adolescent↗

PubMed1999

A novel case of multiple endocrine neoplasia type 2A associated with two de novo mutations of the RET protooncogene.

We report a novel case of multiple endocrine neoplasia type 2A (MEN 2A) associated with two mutations of the protooncogene RET. One affects codon 634 and causes a cysteine to arginine substitution; the second at codon 640 causes an alanine to glycine substitution in the transmembrane region. The two mutations were present on the same RET allele and were detected in germline and tumor DNA. Both mutations were de novo, i.e. they were not found in the DNA of the parents or relatives. Immunohistochemical and RT-PCR analysis showed that the pheochromocytoma expressed calcitonin as well as both RET alleles. A cell line established from the tumor and propagated in culture sustained the expression of RET and calcitonin, as did the original pheochromocytoma. Because the patient presented with medullary thyroid carcinoma and pheochromocytoma without parathyroid gland involvement, we speculate that this clinical picture could be correlated with the two RET mutations and to the unusual calcitonin production. This is the first report of a MEN 2A case due to two mutations of the RET gene and associated with a calcitonin-producing pheochromocytoma.

Adrenal Gland Neoplasms↗

PubMed2003

Acceptable age for prophylactic surgery in children with multiple endocrine neoplasia type 2a.

AIMS: Germline mutated RET proto-oncogene, causing multiple endocrine neoplasia (MEN)-2a syndrome is the indication for prophylactic total thyroidectomy. Literature regarding the risk and the extent of early surgical intervention is scarce and the optimum age for surgery is still controversial. To optimize management in these young children we evaluate our experience and results. PATIENTS AND METHODS: From 1990 to 2001 preventive total thyroidectomy was performed in 13 MEN-2a gene carriers (4 boys and 9 girls; median age 7 (4-14) years). Preoperative assessment, surgical procedure, pathological examination, postoperative complications and treatment results were studied. RESULTS: Surgery existed of a total thyroidectomy alone (n=3) in children with normal basal calcitonin and in combination with tracheo-esophageal exploration (n=6) or central compartment dissection (n=4) in case of abnormal calcitonin levels. Eight children presented with medullary thyroid cancer (MTC), three (median: 5 (4-12) years) with microscopic MTC and five (median 6 (4-14) years) with frank invasive MTC. Four of these five patients were younger than 6 years. Except for long-lasting hypoparathyroidism in one patient there were no complications. At a median follow-up of 6.5 years all patients are disease free. CONCLUSION: MTC in RET mutated MEN-2a gene carriers in childhood are found at the age of 4 years. Therefore, DNA testing should be done preferably before that age. Preventive surgery can be performed safely at that age and may be limited to total thyroidectomy when baseline calcitonin levels are normal.

Adolescent↗

PubMed2006

Estimated risk of pheochromocytoma recurrence after adrenal-sparing surgery in patients with multiple endocrine neoplasia type 2A.

HYPOTHESIS: Adrenal-sparing adrenalectomy is considered the treatment of choice for hereditary bilateral pheochromocytoma in patients with multiple endocrine neoplasia type 2A (MEN 2A). DESIGN: Retrospective analysis of prospectively documented data with a mean +/- SD follow-up of 81.5 +/- 85.3 months. The PubMed database was searched for articles published between 1975 and 2004 to identify published series and/or case reports. SETTING: University hospital referral center. PATIENTS: In 17 (22%) of 77 patients with various mutations of the RET proto-oncogene, unilateral (n = 12) or bilateral (n = 5) pheochromocytomas were documented at the time of diagnosis or during the course of MEN 2A. Adrenal-sparing surgery was performed in 13 patients (group 1), synchronous bilateral total adrenalectomy in 4 patients (group 2A), and metachronous bilateral total adrenalectomy in 5 patients after adrenal-sparing adrenalectomy (group 2B). MAIN OUTCOME MEASURES: Measurement of 24-hour urinary catecholamine levels (noradrenaline, adrenaline, and dopamine) and, in case of high catecholamine levels, imaging studies to localize the tumors in 1 or both adrenal glands to determine the size and exclude extra-adrenal tumors and distant metastasis. RESULTS: The mean+/-SD estimated 5- and 10-year cumulative risk of developing recurrence in both groups was 38.5% +/- 15.7%. Five (38%) of 13 patients in group 1 developed recurrence in the contralateral gland. Two (22%) of 9 patients in groups 2A and 2B developed several episodes of an addisonian crisis, 1 of whom died. CONCLUSIONS: Substantial morbidity and mortality are associated with addisonian crisis after bilateral adrenalectomy. Adrenal-sparing adrenalectomy and close monitoring of the remnant may be the treatment of choice for hereditary bilateral pheochromocytoma in MEN 2A, since overall recurrence is low.

Adrenal Gland Neoplasms↗

PubMed1998

Risk and penetrance of primary hyperparathyroidism in multiple endocrine neoplasia type 2A families with mutations at codon 634 of the RET proto-oncogene. Groupe D'etude des Tumeurs à Calcitonine.

Germline mutations of the RET proto-oncogene are responsible for multiple endocrine neoplasia type 2, including multiple endocrine type 2A (MEN 2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma. The relationship between specific mutations and syndromic features has been established. In particular, the risk for pheochromocytoma and hyperparathyroidism (HPT) in MEN 2A patients is clearly associated with the presence of the RET mutation at a specific position, i.e. at codon 634. Also, a correlation between a specific mutation, C634R, and the development of HPT has been suggested but is still controversial. To further investigate the relationship between specific mutations of codon 634 and the development of HPT, we studied a population of 188 individuals, carrying mutations at codon 634, namely C634R (65 patients belonging to 10 families), C634Y (80 patients belonging to 11 families), or the less frequent codon 634 mutations [i.e. C634S, C634F, C634G, or C634W (43 patients belonging to 9 families)]. In this series of patients, we defined an overall HPT prevalence of 19.1% and found that this prevalence did not vary significantly, with respect to the nature of the mutation. However, irrespective of the particular mutation, the prevalence of HPT showed a high interfamilial variability. The statistical model that best fitted with the observed data was in favor of the heterogeneity of the risk for HPT, with 40% of the families showing an HPT risk of 34% and 60% of the families showing an HPT risk of 9%. In addition, our study clearly demonstrated that HPT could be an early component of the disease and provided the first estimate of age-specific and mutation-specific HPT penetrance in individuals with mutations of codon 634 of the RET proto-oncogene.

Adult↗

PubMed1988

The clinical outcome of prospective screening for multiple endocrine neoplasia type 2a. An 18-year experience.

An important question facing physicians who care for families with multiple endocrine neoplasia type 2a is whether prospective screening to detect early abnormalities of the thyroid, parathyroid, or adrenal glands favorably influences the ultimate course of the disease. An 18-year study of a large family has allowed us to examine the effect of early treatment on the clinical course of the disease. Of 22 patients who underwent thyroidectomy for early C-cell abnormalities, 19 remained free of detectable medullary thyroid carcinoma according to all criteria, at a mean of 11 years after thyroidectomy. None of the 22 patients had evidence of parathyroid disease either at the time of surgery or after a mean follow-up of 10 years. Prospective screening for adrenal medullary abnormalities by means of measurement of 24-hour urinary epinephrine excretion and the ratio of urinary epinephrine to norepinephrine was predictive of pheochromocytoma in 10 of 11 patients (with a false negative result in one patient) but was not useful in diagnosing adrenal medullary hyperplasia. We conclude that regular, prospective screening and early treatment of the manifestations of multiple endocrine neoplasia can prevent metastasis of medullary thyroid carcinoma and the morbidity and mortality caused by pheochromocytoma.

Adrenal Gland Neoplasms↗