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.     

Prenatal molecular diagnosis of RET proto-oncogene mutation in multiple endocrine neoplasia type 2A

We report a case of multiple endocrine neoplasia type 2A (MEN 2A) diagnosed prenatally at 16 weeks gestation. The 35-year-old mother is a MEN 2A patient. She had had three prior pregnancies: one resulted in a stillbirth; one produced a genetically unaffected boy; and the third was terminated in the first trimester owing to a diagnosis of blighted ovum. Autopsy did not reveal the cause of death of the stillborn infant, who was also found to be affected with MEN 2A by molecular study of paraffin-embedded tissue. Because of poor obstetric history and the patient's age, amniocentesis for cytogenetic and molecular studies was performed at 16 weeks' gestation during the pregnancy under discussion. As with other affected members in the mother's family, the missense mutation of TGC to TTC at codon 634 of the RET proto-oncogene was found in amniotic fluid cells. Analysis of DNA extracted from the lymphocytes of the infant's blood at birth confirmed the diagnosis. To our knowledge, this is the first report of prenatal diagnosis of MEN 2A.     

The molecular pathology of RET protooncogene in families with multiple endocrine neoplasia type 2A

BACKGROUND: Multiple endocrine neoplasm type 2A (MEN 2A) is an autosomal dominantly inherited disease characterized by medullary thyroid carcinoma, pheochromocytoma and hyperparathyroidism. Mutations have been identified in the extracellular domain of the RET proto-oncogen product (10q11.2) in MEN 2A patients. In each case a single base pair substitution results in replacement of cysteine with another amino acid. Most MEN 2A patients have mutations of codon 634. PATIENTS AND METHODS: Sixty-five unrelated MEN 2A patients from seven families were studied. Polymerase chain reaction, segregation, sequence analysis and restriction enzyme digestion were performed. RESULTS: Of seven families, four had the TGC to TAC transition, two families the TGC to TGG transversion and one family the TGC to CGC transition in codon 634 of RET. CONCLUSIONS: We found all the mutations in codon 634. The characterization of MEN 2A mutations allows early and presymptomatic diagnosis in this syndrome.     

Molecular tools for presymptomatic testing in multiple endocrine neoplasia type 1

This study sought to determine the prevalence of upper-extremity musculoskeletal disorders (UEMSDs) among keyboard operators in Sao Paulo, Brazil, and to compare this prevalence with that among other office workers. One hundred and thirty keyboard operators (mean age 33 years, 60 male/70 female) and 138 office workers (mean age 35 years, 82 male/56 female) from two computing centers were interviewed by a research assistant using a standardized questionnaire. Symptomatic subjects, defined as those who reported upper extremity pain or lost work time due to pain in the preceding 12 months, were examined by a rheumatologist. Mean (SD) lengths of employment were 9 (6) years for keyboard operators and 8 (6) years for office workers. Upper-extremity pain during the preceding seven days was reported by 66 keyboard operators (51%) and by 18 office workers (13%) (p < 0.0001); during the preceding 12 months, by 90 keyboard operators (69%) and by 26 office workers (19%) (p < 0.0001). UEMSDs were diagnosed following physical examination in 50 keyboard operators and in 12 office workers (9%) (p < 0.0001). Tenosynovitis was the most common disorder diagnosed among the keyboard operators (n = 23). Among the keyboard operators the prevalence of UEMSDs was significantly lower for males (p = 0.017, OR = 0.38, 95%CI = 0.17-0.86). The presence of a diagnosed UEMSD was significantly associated with duration of employment (p = 0.005) and lack of or insufficient rest breaks (p = 0.012). Keyboard operators had significantly more UEMSDs than did office workers. Strategies aimed at the reduction of repetitive strain injuries among keyboard operators, such as the provision of adequate work breaks, should be evaluated.     

RET protooncogene mutational analysis in multiple endocrine neoplasia syndrome type 2B: case report and review of the literature

Multiple endocrine neoplasia, type 2B (MEN 2B), is a phenotypic variant of a group of autosomal-dominant neurocristopathies. MEN 2B is associated with medullary thyroid carcinoma and pheochromocytoma with oral, ocular, and alimentary submucosal ganglioneuromas and Marfanoid body features. Approximately 50% of cases are thought to be spontaneous mutations. The RET protooncogene (RET) is a 21-exon gene encoding a tyrosine kinase receptor. A codon 918 germ line mutation, which converts a highly conserved methionine to a threonine in the intracellular tyrosine kinase portion of this receptor of RET, has been identified in 95% of patients with MEN 2B. This mutation is easily detected by a direct deoxyribonucleic acid sequencing or restriction enzyme (Fok 1) analysis of amplified polymerase chain reaction products. The RET gene is normally expressed in the oral and gastrointestinal submucosal neural ganglia, and the codon 918 mutation is thought to cause neuromas by virtue of its transforming activity in these ganglia. Identifying clinical features of MEN 2B in an 11-year-old boy by an oral pathologist led to confirmation by mutational analysis. Before genetic testing was available, the patient, and at a later date his mother, underwent thyroidectomies based solely on biochemical testing. Results indicated the patient had the codon 918 mutation, whereas his phenotypically normal mother, father, and older brother had normal RET analyses. Studies in families have demonstrated that the mutant allele is derived from the father with possible acquisition during spermatogenesis. We believe the mother of our affected patient to be normal; the absence of phenotypic features of MEN 2B and a normal genotype suggest her calcitonin abnormalities and minimal evidence for C-cell hyperplasia were inconsequential. Molecular analysis for RET abnormalities will likely supplant biochemical methods of diagnosis in patients with MEN 2B.     

Importance of endocrine imaging methods in multiple endocrine neoplasia type 2A proved by mutation analysis

Multiple endocrine neoplasias are rare, inherited disorders. The authors describe a case history of a patient with multiple endocrine neoplasia type 2A, who presented with unusual clinical manifestations. The diagnosis of phaeochromocytoma, which was the first manifestation of the disorder, was greatly facilitated with radiologic imaging methods. The authors review, on the basis of recent data from the literature, the importance of radiologic methods, which improved due to methodological advance. Finally, the authors emphasize the importance of follow-up for early diagnosis.     

Germline dinucleotide mutation in codon 883 of the RET proto-oncogene in multiple endocrine neoplasia type 2B without codon 918 mutation

The autosomal dominant multiple endocrine neoplasia type 2 syndromes (MEN 2) comprise three clinically distinct entities, MEN 2A, familial medullary thyroid carcinoma and MEN 2B, which share a common clinical feature: medullary thyroid carcinoma (MTC). MEN 2B is considered to have the most aggressive form of MTC. Therefore, early detection of MEN 2B in order to prevent potentially lethal MTC is important. More than 95% of all MEN 2B cases are caused by germline mutation at codon 918 (M918T) in exon 16 of the RET proto-oncogene. In this study, we demonstrate the presence of germline codon 883 mutation (A883F) in 2 of 3 unrelated MEN 2B cases without codon 918 mutation. Our data demonstrate a novel etiologic event which may have roles in predisposition to MEN 2B when present in the germline and in the pathogenesis of sporadic MTC when somatic.     

Multiple endocrine neoplasia associated with multiple lipomas

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN-1) is characterized by tumors of the parathyroids, the neuroendocrine pancreas-duodenum and the anterior pituitary, but shows also a wide clinical variety of other symptoms. CASE REPORT: We present a case of a 68-year-old woman with a 18 year history of MEN-1 consisting of gastrinoma and primary hyperparathyroidism. Beside these typical symptoms, the patient suffered from thyroid adenoma, malignant kidney tumor and multiple subcutaneous lipomas. RESULT: While the number of autopsies declined from 113 in 1977 to 66 in 1984, the number of diagnostic techniques used increased continuously (94, 107, 118 and 140, amounting to 0.83, 1.34, 1.76 and 2.12 per patient). The premortal detection of abdominal abnormalities increased globally from 16.8 to 32.5%. This increase was largely due to better diagnosis of liver and gallbladder abnormalities which were in most cases of little relevance. CONCLUSION: Whether these non-endocrine tumors are associated to MEN-1 is unclear and has to be tested by examining the chromosomal regions 11q13 and 11q24/25 of the tumors sample, in which the possible MEN-1 involved tumor suppressor genes are located.     

Surgical management of primary hyperparathyroidism in multiple endocrine neoplasia types 1 and 2

BACKGROUND: The surgical management of primary hyperparathyroidism in multiple endocrine neoplasia type 1 (MEN 1) remains controversial. In addition, the rarity of MEN 2A-related hyperparathyroidism has not allowed for a separate strategy for this condition. This study examines our surgical experience with MEN 1- and MEN 2A-related hyperparathyroidism and attempts to define a rational therapeutic approach to each. METHODS: Between 1970 and 1991, 124 patients underwent surgery for MEN-related hyperparathyroidism at our institution. Primary cervical explorations were performed in 84 patients with MEN 1 and 18 with MEN 2A. An additional 22 patients with MEN 1 underwent reoperative surgery. All patients with MEN 2A underwent concomitant thyroidectomy for medullary thyroid cancer. RESULTS: Compared with patients with MEN 1, patients with MEN 2A, had a lower preoperative serum Ca2+ level and fewer symptoms or complications of hypercalcemia. Multiple gland disease was evident in 90% and 83%, respectively, of patients with MEN 1 and MEN 2A. Primary explorations in patients with MEN 1 resulted in surgical cure in 94%, persistent hypercalcemia occurring in no patient undergoing subtotal resection compared with 17% of patients in whom more conservative resections were performed (p = 0.005). In patients with MEN 1, 10-year recurrence of hypercalcemia was 16% for primary explorations and 30% for reoperative procedures. In contrast, all patients with MEN 2A, whether treated by total, subtotal, or lesser resections, were cured after surgery and none had recurrence during a median follow-up of 5.8 years. CONCLUSIONS: In MEN 1 the surgical principles should be (1) identification of all four glands, (2) subtotal resection to ensure cure and facilitate possible reoperation, and (3) excision of supernumerary thymic glands. In MEN 2A we should identify and resect all enlarged glands for cure, but routine subtotal resection need not be performed because this condition is readily cured and recurrence is rare.     

Genetic testing in presymptomatic diagnosis of multiple endocrine neoplasia

Multiple endocrine neoplasias (MEN) are familial diseases characterized by endocrine neoplasms and transmitted in an autosomal dominant manner. In MEN type 1, the major lesions affect parathyroid glands, pancreatic islet cells and anterior pituitary. The MEN-1 gene has been mapped to chromosome 11q13 and a set of DNA-polymorphic markers localized close to this region provides a useful tool for presymptomatic diagnosis in MEN-1 families. MEN type 2 refers to the inherited forms of medullary thyroid carcinoma (MTC) associated or not with pheochromocytoma and hyperparathyroidism. In MEN-2, germinal mutations of the C-RET proto-oncogene which is localized on chromosome 10q11 have been found in the three clinical and allelic forms of the syndrome respectively, MEN-2 type A, B and familial isolated MTC. Mutations of C-RET are found in more than 90% of MEN-2 patients and genetic screening leads to accurate risk evaluation in families and consequently a preventive treatment of MTC and adrenal neoplasms. Recent discoveries on MEN syndromes and related familial endocrine disorders have a major clinical impact and allow a better understanding of the physiological pathways involved in familial as well as in sporadic endocrine tumor pathogenesis.     

Characteristic pathological associations in multiple endocrine neoplasia type 1

OBJECTIVES: Multiple endocrine neoplasia type 1 (MEN 1) is an inherited disorder characterised by slow progressing tumors of the parathyroids, of the endocrine pancreas and of the anterior pituitary. A genetic locus predisposing to this disease has been localised on chromosome 11. Predictive diagnosis of carriers of the defective gene is possible in families using genetic markers at this locus. However, this analysis presupposes a precise identification of affected subjects. Moreover, expression of the disease may vary from one family to the other. The aim of the present study was to define the typical clinical features of the syndrom. METHODS: We assessed retrospectively 26 cases of MEN 1 identified during 20 years in the same medico-surgical center. Among 11 men and 15 women, all those who had a genealogical investigation had a positive family history of MEN 1. RESULTS: Bifocal and trifocal tumors were the main patterns of associations, and were diagnosed at a mean age of 48.6 years. Parathyroid involvement was most frequent and earliest (96% of cases). The second most frequent was pancreatic involvement (69.2% of cases) predominantly manifesting with gastrinomas (N = 13). Multifocal tumors were usually diagnosed before or within 5 years following diagnosis of the first tumor. Among pituitary tumors one case of meningioma was observed, a feature not reported previously. An asymptomatic adrenal involvement was observed in about 1/3 of cases. Other silent tumors (euthyroid nodules, lipomas) were also noted. CONCLUSION: These data suggest that the clinical presentation and course of MEN 1 is homogeneous and are in agreement with the hypothesis of a recessive tumor-suppressor gene expressed in specific endocrine cell lines, suggesting that careful family studies should be conducted when a case of MEN 1 is diagnosed to facilitate early carrier detection among relatives.     

Genetic testing in multiple endocrine neoplasia and related syndromes

The complete assignment of the proton chemical shifts obtained by nuclear magnetic resonance (NMR) spectroscopy of de-O-acetylated glucuronoxylomannans (GXMs) from Cryptococcus neoformans permitted the high-resolution determination of the total structure of any GXM. Six structural motifs based on an alpha-(1-->3)-mannotriose substituted with variable quantities of 2-O-beta- and 4-O-beta-xylopyranosyl and 2-O-beta-glucopyranosyluronic acid were identified. The chemical shifts of only the anomeric protons of the mannosyl residues served as structure reporter groups (SRG) for the identification and quantitation of the six triads present in any GXM. The assigned protons for the mannosyl residues resonated at clearly distinguishable positions in the spectrum and supplied all the information essential for the assignment of the complete GXM structure. This technique for assigning structure is referred to as the SRG concept. The SRG concept was used to analyze the distribution of the six mannosyl triads of GXMs obtained from 106 isolates of C. neoformans. The six mannosyl triads occurred singularly or in combination with one or more of the other triads. The identification and quantitation of the SRG were simplified by using a computer-simulated artificial neural network (ANN) to automatically analyze the SRG region of the one-dimensional proton NMR spectra. The occurrence and relative distribution of the six mannosyl triads were used to chemotype C. neoformans on the basis of subtle variations in GXM structure determined by analysis of the SRG region of the proton NMR spectrum by the ANN. The data for the distribution of the six SRGs from GXMs of 106 isolates of C. neoformans yielded eight chemotypes, Chem1 through Chem8.     

Distinct multiple RET/PTC gene rearrangements in multifocal papillary thyroid neoplasia

Rearrangements involving the RET protooncogene have been implicated in the development of papillary thyroid carcinoma (PC). Transgenic mice, expressing thyroid-targeted RET/PTC-1, develop PC; but the clinical significance of this oncogene remains uncertain. We examined the expression of RET/PTC-1, -2, and -3 in human thyroid microcarcinomas and clinically evident PC to determine its role in early stage vs. developed PC and to examine the diversity of RET/PTC in multifocal disease. RNA was extracted from paraffin-embedded microcarcinomas and clinically evident PCs; the results obtained from paraffin-embedded tissue were confirmed on RNA from corresponding snap-frozen tissue of clinically evident PCs. RT and PCR was performed using primers for RET/PTC-1, -2, and -3; PGK-1 (the housekeeping gene) analysis was used to ensure integrity of the RNA and efficiency of the RT reaction. PCR products were resolved by gel electrophoresis, and Southern hybridization was performed with RET/PTC-1, -2, and -3 probes. A polyclonal antibody to the carboxyterminus of RET was used for immunohistochemistry on paraffin sections. Thirty-nine occult papillary thyroid microcarcinomas from 21 patients were analyzed. Of the 30 tumors (77%) positive for RET/PTC rearrangements, 12 were positive for RET/PTC-1, 3 for RET/ PTC-2, 6 for RET/PTC-3, and 9 for multiple RET/PTC oncogenes. In clinically evident tumors, 47% had RET/PTC rearrangements. Immunohistochemistry demonstrated close correlation with RT-PCR-derived findings. RET/PTC expression is highly prevalent in microcarcinoma and occurs more frequently than in clinically evident PC (P < 0.005). Multifocal disease, identified in 17 of the 21 patients, exhibited identical RET/PTC rearrangements within multiple tumors in only 2 patients; the other 15 patients had diverse rearrangements in individual tumors. Our results indicate that RET/PTC oncogene rearrangements may play a role in early-stage papillary thyroid carcinogenesis, but they seem to be less important in determining progression to clinically-evident disease. In multifocal disease, the diversity of RET/PTC profiles, in the majority of cases, suggests that individual tumors arise independently in a background of genetic or environmental susceptibility.     

Surgical strategy for insulinomas in multiple endocrine neoplasia type I

An unusual presentation of a giant intracranial aneurysm is demonstrated. The patient was a 58-year-old woman who developed sudden onset of headache followed by generalized seizures. CT scan showed a high-density lesion in the middle cranial fossa with extensive vasogenic edema. Possible mechanisms for the edema are discussed.     

Mutation analysis of glial cell line-derived neurotrophic factor, a ligand for an RET/coreceptor complex, in multiple endocrine neoplasia type 2 and sporadic neuroendocrine tumors

Causative germline missense mutations in the RET proto-oncogene have been associated with over 92% of families with the inherited cancer syndrome multiple endocrine neoplasia type 2 (MEN 2). MEN 2A is characterized primarily by medullary thyroid carcinoma (MTC) and pheochromocytoma, both tumors of neural crest origin. Parathyroid hyperplasia or adenoma is also seen in MEN 2A, but rarely in MEN 2B, which has additional stigmata, including a marfanoid habitus, mucosal neuromas, and ganglioneuromatosis of the gastrointestinal tract. In familial MTC, MTC is the only lesion present. Somatic RET mutations have also been identified in a subset of sporadic MTCs, pheochromocytomas, and rarely, small cell lung cancer, but not in sporadic parathyroid hyperplasias/adenomas or other neuroendocrine tumors. Glial cell line-derived neurotrophic factor (GDNF) and its receptor molecule GDNFR-alpha, have recently been identified as members of the RET ligand binding complex. Therefore, the genes encoding both GDNF and GDNFR-alpha are excellent candidates for a role in the pathogenesis of those MEN 2 families and sporadic neuroendocrine tumors without RET mutations. No mutations were found in the coding region of GDNF in DNA samples from 9 RET mutation negative MEN 2 individuals (comprising 6 distinct families), 12 sporadic MTCs, 17 sporadic cases of parathyroid adenoma, and 10 small cell lung cancer cell lines. Therefore, we find no evidence that mutation within the coding regions of GDNF plays a role in the genesis of MEN 2 and sporadic neuroendocrine tumors.     

Absence of rectoanal inhibitory reflex in a child with multiple endocrine neoplasia type 2B

BACKGROUND: Patients with multiple endocrine neoplasia (MEN) type 2B inherently present with gastrointestinal motility disorders as well as medullary thyroid carcinoma, adrenal pheochromocytoma, and Marfanoid habitus. METHODS: The authors examined gut motility function in a 7-year-old girl with MEN type 2B who had suffered from chronic constipation and recurrent acalculous cholecystitis since infancy. RESULTS: Results of total gastrointestinal barium meal and enema studies showed marked hypoperistalsis of the gut and entire colonic dilatation. Histopathologic study results of the gut wall from the stomach, duodenum, and rectum showed hyperplasia of the submucosal and intramuscular neural plexuses in all specimens. Anorectal manometry demonstrated disarrangement of the internal sphincter rhythmic wave and a complete absence of the rectoanal inhibitory reflex. CONCLUSION: These data suggest that gut motility disorders in MEN type 2B are caused by inadequately organized autonomic nervous system activity that originates from hyperplasia of the enteric nervous system.     

Multiple endocrine neoplasia syndrome, type 2B

It was investigated whether there is a seasonal variation in sex ratio at birth in Germany. The analysis was based on records from the German Bureau for Statistics, covering the period from 1946 to 1995. A highly significant (P < or = 0.001), albeit low-amplitude rhythm was found with two peaks in May and December, and two nadirs in March and October. No correlations were found between sex ratios and seasonal birth rates during this period.     

Aggressive forms of gastric neuroendocrine tumors in multiple endocrine neoplasia type I

In recent classifications of gastric endocrine tumors, tumors arising in patients with multiple endocrine neoplasia type 1 (MEN-1) are regarded to be regulated by the concomitant hypergastrinemia resulting from to pancreatic or, most commonly, duodenal gastrinomas and to have a benign behavior. In this article, we report on two cases of MEN-1 gastric neuroendocrine tumors having a fatal course. Case 1 was a young male with hyperparathyroidism and Zollinger-Ellison syndrome and with florid development of multiple gastric carcinoids and multiple duodenal gastrinomas. Metastases occurred in the liver, of exclusive gastric origin, in periduodenal lymph nodes, of exclusive duodenal origin, and in perigastric lymph nodes, of mixed origin. The patient died 48 months after diagnosis. Case 2 was an adult female patient with hyperparathyroidism, adrenocortical disorders, and gastric tumors but no hypergastrinemia. The patient died 3 months after tumor diagnosis. At autopsy, the stomach showed multiple benign carcinoids and two independent neuroendocrine carcinomas not reported before in MEN-1 and massively metastatizing to lymph nodes, liver, and peritoneum. Multiple islet cell tumors mostly producing pancreatic polypeptide were found, whereas gastrinomas were seen in neither the pancreas nor the duodenum. Allelic losses at the MEN-1 gene locus in chromosome 11q13, the mechanism responsible for tumor development in MEN-1 syndrome, were demonstrated in the carcinoid tumors of case 1 and in the neuroendocrine carcinoma of case 2. We conclude that gastric neuroendocrine tumors in patients with MEN-1 may have a poor outcome, they have the same genetic mechanism as MEN-1 tumors in other organs, and they may be independent of the trophic effect of hypergastrinemia.