Glucagonoma syndrome presenting as psoriasis.
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Adult↗
Biomedical subjects
E Dow
Publications and source records attributed to E Dow.
High prevalence of primary aldosteronism in the Tayside hypertension clinic population.
Primary aldosteronism (PA) was thought to be rare but recent evidence from Australia suggests that it may be more common. As this has important implications in terms of hypertension management, we undertook to screen for this treatable condition in our hypertension clinic. We obtained blood samples in sequential patients referred for assessment in our hypertension clinic in Tayside for plasma renin activity (PRA) and aldosterone. The aldosterone to PRA ratio (ARR) was used as an initial screening test to identify potential patients with PA. Those patients with an elevated ratio (> or =750) were admitted for the salt loading and fludrocortisone suppression test. These patients also underwent adrenal CT scanning, and in selected patients, adrenal scintigraphy. Between May 1995 and January 1997 (21 months), we screened a total of 495 patients. ARR was available in 465 (93.9%) patients. Out of that number, 77 (16. 6%) had an elevated ratio of > or =750, five of whom had an adrenal adenoma (one had previous adrenalectomy). Forty-five of these patients were admitted for the salt loading and fludrocortisone suppression test with 41 positive test results suggesting PA. One patient with a negative salt loading test result however had an adenoma proven on histology. A total of 43 cases of PA were identified, giving a minimum prevalence of 9.2% (43/465). Potentially the prevalence may be up to 15% assuming that the ARR has a sensitivity of 93% (42/45) in predicting PA. In conclusion, about one in 10 patients attending a hypertension clinic may have PA. This suggests that the prevalence of PA in Tayside is as high as that in the Australian hypertensive population, and this is likely to be true elsewhere, with obvious important implications for hypertension management.
Adult↗
Combined paclitaxel, cisplatin, and etoposide for patients with previously untreated esophageal and gastroesophageal carcinomas.
BACKGROUND: Paclitaxel (T), etoposide (E), and cisplatin (P) are each active in gastric carcinoma, either as single agents or as part of a multidrug regimen. To the authors' knowledge, the combination of these three agents in the treatment of patients with esophageal or gastroesophageal carcinoma has not been previously studied. METHODS: Previously untreated patients with locally advanced carcinoma of the stomach, esophagus, or gastroesophageal (GE) junction received at least 2 cycles of TPE administered twice weekly for 3 weeks, with the cycle repeated every 28 days. Drug doses, administered over 3 hours on either Monday and Thursday or Tuesday and Friday, consisted of T 50 mg/m2/dose, P 15 mg/m2/dose, and E 40 mg/m2/dose. For patients with local disease only, subsequent therapy consisted of radiation with or without surgical resection. RESULTS: Twenty-five patients with gastric (10) or gastroesophageal or GE junction (15) carcinoma were treated. Eighteen had locally advanced disease and 7 had liver metastases at presentation. Hematologic toxicity, namely, Grade 3 anemia and neutropenia, was experienced by all patients. The median number of treatment cycles was 4 (range, 2-6). Three patients were not evaluable for response. All 22 evaluable patients responded; 3 were complete responders and 19 were partial responders. Eleven patients received radiation therapy with (6) or without (5) concomitant 5-fluorouracil, and 8 patients subsequently underwent surgical resection. Three of 8 patients had no tumor at surgery, 4 had minimal microscopic tumor at the primary site, and 3 had microscopic lymph node involvement. Twenty-three patients are alive, of whom 14 are without evidence of disease. Two patients with metastatic disease at presentation died at 9 and 29 months, respectively. The median survival was 12.5 months (range, 6 to 30+ months). CONCLUSIONS: Multifractionated TPE chemotherapy is a highly active regimen in gastric and gastroesophageal carcinoma. It could be evaluated in Phase III trials against other active regimens for the treatment of patients with this disease. The introduction of 5-fluorouracil could also be an interesting direction to explore because of its primary role in the treatment of patients with gastric and esophageal carcinoma.
Adult↗
The multifractionated, twice-weekly dose schedule for a three-drug chemotherapy regimen: a phase I-II study of paclitaxel, cisplatin, and vinorelbine.
BACKGROUND: Paclitaxel, cisplatin, and vinorelbine are three important antineoplastic drugs with different mechanisms of cell kill. A combination of these three drugs potentially could have additive therapeutic effects. METHODS. The three-drug combination (designated TPN) was administered on a twice-weekly (Monday/Thursday; Tuesday/Friday) schedule for 3 weeks, with cycles repeated every 28 days. The Phase I design utilized a dose de-escalation schema in which the maximum tolerated dose was defined by a patient's ability to complete 6 doses (a full cycle) without interruption for hematologic Grade 3 or 4 toxicity. RESULTS: Twenty-seven patients received a total of 42 evaluable courses of the 3-drug regimen. The cisplatin dose was fixed at 15 mg/M2/fraction. The paclitaxel dose was first fixed at 50 mg/M2/fraction, and venorelbine was delivered at 3 dose levels per fraction: 10, 7.5, and 5 mg/M2. Paclitaxel then was de-escalated to 40 mg/M2/fraction, and the same 3 dose levels of vinorelbine were evaluated. The dose-limiting toxicity was neutropenia. Using fixed doses of paclitaxel at 40 mg/ M2/fraction and cisplatin at 15 mg/M2, the optimal dose fraction for vinorelbine was 7.5 mg/M2, defined as the dose that allowed > 67% of patients to complete 3 weeks (6 consecutive doses) of therapy. Using paclitaxel at 50 mg/M2/fraction (cisplatin at 15 mg/M2/fraction), the optimal dose of vinorelbine was 5 mg/M2/fraction. Tumor responses were observed in 13 patients: 2 with unknown primary, 1 with esophageal carcinoma, 6 with nonsmall cell lung carcinoma, and 3 with breast carcinoma. Grade 2 neurologic (sensory) toxicity was observed in 5 patients. CONCLUSIONS: TPN administered according to a twice-weekly dosing scheme can be delivered with acceptable toxicity. The dose intensity for paclitaxel (60-75 mg/M2/week), cisplatin (22 mg/M2/week), and vinorelbine (15 mg/M2/week) is > 50% of the single agent dose intensity for the component agent. Recommended Phase II or Phase III trials could utilize dose fractions of paclitaxel, cisplatin, and vinorelbine at either 50, 15, and 5 mg/M2/fraction or 40, 15, and 7.5 mg/M2/fraction in this twice-weekly, multifractionated dose schedule.
Adult↗
Phase I-II trial of 14 day infusional 6-mercaptopurine in advanced colorectal cancer.
6-Mercaptopurine (6-MP) is a cycle specific antineoplastic agent with a short serum half-life following bolus administration, providing a rationale for continuous infusional administration of the parenteral formulation. 22 patients received 38 courses of 14 day 6-MP infusion. The maximum tolerated dose (MTD) was 35 mg/m2/day (total dose per 14 day cycle 490 mg/m2) with cycles repeated at 28 days. Toxicities included transient hyperbilirubinaemia, leucopenia and thrombocytopenia. 13 evaluable patients with advanced colon cancer resistant to 5-fluorouracil with or without leucovorin received infusional 6-MP at the MTD as part of the phase II study analysis, but no objective responses were observed. Phase II studies in previously untreated patients and longer infusion durations are being evaluated.
Adult↗
Paclitaxel, cisplatin, etoposide combination chemotherapy: a multifractionated bolus dose schedule for non-small cell lung cancer.
In this phase II study, paclitaxel was added to the combination of cisplatin and etoposide (TPE regimen), in 37 patients with advanced non-small cell lung cancer, using a multifractionated dosing schedule. The total dose of paclitaxel (175-200 mg/m2); cisplatin (75 mg/m2); and etoposide (175-200 mg/m2) was divided into five daily doses administered over 3 h with cycles repeated at 21-28 days. 15 patients had stage III A or B disease and 22 stage IV disease. 32 patients were evaluable for toxicity and 37 for response. Neutropenia was the most prominent toxicity. Grade 3 or grade 4 neutropenia was observed in 12 (38%) and 9 (25%) of the patients, respectively and 11 patients required hospitalisation. 3 patients died secondary to chemotherapy related sepsis. Diarrhoea (grade 3, 3 patients; grade 4, 2 patients) was the only other significant non-haematological acute toxicity. The optimal dose rate for this multifractionated regimen was paclitaxel 35 or 40 mg/m2/fraction; cisplatin 15 mg/m2/fraction; etoposide 35 or 40 mg/m2/fraction. Responses were observed in 28 of 37 evaluable patients (3 complete response; 25 partial responses [76%]. 22 patients are alive; 8 with stage III B disease received radiation or surgery (3 had minimal or no tumour in the pathology specimen). TPE is a highly active regimen for non-small cell lung cancer and multifractionated dose scheduling is a feasible and well tolerated system.
Adult↗
Paclitaxel, cisplatin and etoposide combination chemotherapy: a comparison of dose intensity in two multifractionated dose schemas.
66 patients with a variety of tumour types received the multifractionated TPE three drug regimen in a non-random allocation as a 5 day schedule (schedule A) or as a twice weekly schedule (schedule B). The dose per fraction for each component drug was 35, 40 or 50 mg/m2 for both paclitaxel and etoposide and for cisplatin, the dose per fraction was 15 mg/m2. The total paclitaxel and etoposide dose was 175, 200, 250 mg/m2 3 week cycle. For schedule A, grade 3 or 4 neutropenia was observed in 70/114 cycles (61%) with two treatment related deaths from 50 treated patients. For schedule B, grade 3 neutropenia was observed in 1 of 30 courses (3%) with one drug related death from 19 treated patients. Dose intensity was increased by 20% for both paclitaxel and etoposide with the twice weekly schedule and at all dose levels, with haematological toxicity substantially reduced relative to schedule A. Using multifractionated schedules, a twice weekly open ended schedule results in an approximately 20% greater dose intensity and less toxicity compared with a 5 day schedule repeated every 3 weeks. The recommended dose schedule for TPE is paclitaxel 40 mg/m2; cisplatin 15 mg/m2 and etoposide 40 mg/m2 twice weekly for 3 weeks repeated every 4 weeks.
Adult↗
Prohormone convertase 1 in obesity, gestational diabetes mellitus, and NIDDM: no evidence for a major susceptibility role.
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Aspartic Acid Endopeptidases↗
Association between beta 2-adrenoceptor polymorphism and susceptibility to bronchodilator desensitisation in moderately severe stable asthmatics.
BACKGROUND: In-vitro studies have suggested that polymorphisms of the beta 2-adrenoceptor may influence the desensitisation induced by beta 2-agonists. We investigated the influence of beta 2-AR polymorphism on the development of bronchodilator desensitisation in asthma patients. METHODS: We carried out an analysis of 22 moderately severe stable asthmatics, mean age 38 years, FEV1 63% of predicted and FEF25-75 38% of predicted, who received a median inhaled corticosteroid dose of 1000 micrograms/day. Patients were randomly assigned inhaled placebo or inhaled formoterol 24 micrograms bid for 4 weeks each in a crossover study. Bronchodilator dose-response curves were made at the end of each treatment period by use of cumulative doses of formoterol (6-108 micrograms) with FEV1 and FEF25-75 measured 30 min after each dose, and up to 6 h after the last dose. We calculated the degree of bronchodilator desensitisation by comparing the dose-response (for maximum and 6 h) after placebo with that after formoterol, and expressed this degree as a percentage of placebo response. Patients were divided into groups according to genotype at codon 16: homozygous Arg 16 (n = 4), heterozygous Arg 16/Gly 16 (n = 8), and homozygous Gly 16 (n = 10). At codon 27: homozygous Gln 27 (n = 5), heterozygous Gln 27/Glu 27 (n = 11), and homozygous Glu 27 (n = 6). FINDINGS: We found a significantly (p < 0.05) greater degree of bronchodilator desensitisation with homozygous Gly 16 than with homozygous Arg 16 for maximal FEV1 response: -8% (Arg 16) vs 46% (Gly 16); and for maximal FEF25-75 response: -32% (Arg 16) vs 74% (Gly 16; 95% CI 15-92% and 49-164%, respectively). Bronchodilator responses at 6 h were also significantly (p < 0.05) different for FEV1 and FEF25-75 when Arg 16 and Gly 16 were compared and values for heterozygous Arg 16/Gly 16 were intermediate. There was significantly greater desensitisation with Glu 27 than with Gln 27 for maximal FEF25-75 response: -7% (Gln 27) vs 68% (Glu 27), p = 0.05; and for 6 h FEF25-75 response: 43% (Gln 27) vs 93% (Glu 27), p < 0.05 (95% CI 2-147% and 5-94%, respectively). All patients who were homozygous Glu 27 were also homozygous Gly 16. INTERPRETATION: We have found preliminary evidence that beta 2-adrenoceptor polymorphism is associated with altered beta 2-adrenoceptor expression in asthma patients. The homozygous Gly-16 form was significantly more prone to bronchodilator desensitisation than Arg 16, with the influence of Gly 16 dominating over any putative protective effects of Glu 27.
Administration, Inhalation↗
Liver function tests in pre-eclampsia: importance of comparison with a reference range derived for normal pregnancy.
OBJECTIVES: To determine reference ranges for liver function tests in uncomplicated pregnancy and to relate abnormal results by these criteria to outcome in pre-eclampsia. DESIGN: Prospective, cross-sectional study to establish the reference ranges. Prospective observational study of women with pre-eclampsia. SETTING: Antenatal clinics and obstetric unit of St Mary's Hospital, London. PARTICIPANTS: Four hundred and thirty women with uncomplicated pregnancies and 85 consecutive women with gestational hypertension. MAIN OUTCOME MEASURES: Aspartate transaminase (AST), alanine transaminase (ALT), bilirubin and gamma glutamyl transferase (GGT) were measured to determine their ranges in normal pregnancy. The severity of pre-eclampsia was determined by the maximum blood pressure, creatinine and 24 h urinary protein; minimum platelet count; maternal complications; mode of and gestation at delivery; and fetal outcome with centile weight adjusted for gestational age and sex. RESULTS: AST, ALT, bilirubin and GGT were each lower in uncomplicated pregnancy than the nonpregnant laboratory reference ranges. Of those cases with elevated liver function tests in the pre-eclampsia group, 37% were abnormal only by the new reference ranges. Using the new ranges, the prevalence of elevated liver function tests was significantly higher in the pre-eclampsia group (54%) than in those with pregnancy induced hypertension (14%) (P < 0.01). Amongst those with pre-eclampsia, abnormal liver function tests were associated with greater proteinuria (P < 0.05), lower platelet count (P < 0.001) and more maternal complications (P < 0.01) than normal liver function tests; there was no difference in the severity of hypertension between the groups. CONCLUSIONS: Liver function tests are lower in normal pregnancy than the reference ranges currently used. Our pregnancy-derived ranges allow more precise identification of abnormal liver function in women with pre-eclampsia than is possible using standard reference ranges derived from a nonpregnant population.
Adolescent↗
Pilot study of ambulatory infusional delivery of a multidrug regimen: ifosfamide, carboplatin and etoposide (ICE).
PURPOSE: To determine the feasibility for administering ICE (ifosfamide, carboplatin, and etoposide) using an ambulatory infusional schedule for each of the three agents in a design that sequentially alternates those agents that are not compatible as an admixture. PATIENTS AND METHODS: Forty-one patients received ICE administered as follows: ifosfamide (500 mg/M2/day) without mesna days 1 to 7 and 14 to 21; carboplatin (30 or 40 mg/M2/day) and etoposide (30 to 40 mg/M2/day) admixed as a single solution infused day 7 to 14. Patients were monitored weekly and cycles repeated at five-week intervals. RESULTS: Seventy-nine courses of therapy were analyzed. Forty-one patients received a median of two cycles with a range of one to five cycles. The only significant toxicity was hematologic with 11 patients experiencing grade III neutropenia and 7 patients grade III thrombocytopenia (18%). Eleven patients did develop significant anemia requiring transfusion and/or the use of erythropoietin. Tumor responses were observed in 7 of 24 evaluable patients, 4 of whom had lung cancer, 2 with small cell with no prior therapy and 2 with nonsmall cell with prior chemotherapy. CONCLUSION: Ambulatory infusion of ICE using an alternating sequence is feasible, and although the dose per cycle of carboplatin and etoposide is less than that of conventional bolus schedules for either single agent or combination programs, the ability to deliver this combination of agents in an ambulatory setting and without mesna substantially reduces the cost. Phase II studies of ambulatory infusion ICE in nonsmall cell lung cancer, lymphoma, and sarcoma are a reasonable next step.
Adenocarcinoma↗
Pilot study of ambulatory infusional delivery of a multidrug regimen: cisplatin, 5-fluorouracil and leucovorin (PFL) +/- etoposide.
PURPOSE: To determine the feasibility of ambulatory infusional administration 24 hours per day, 7 days per week of a three-drug regimen of cisplatin or carboplatin, leucovorin, and 5-fluorouracil (5-FU) (PLF) utilizing an alternating weekly sequential design and to introduce infusional etoposide as PLEF to the regimen. PATIENTS AND METHODS: Forty-three patients with diverse malignancies received a sequential infusion of 5-FU 200 mg/M2/day on days 1 to 14 and 21 to 35 with leucovorin admixed for day 1 to 7 and 21 to 28. Cisplatin (20 patients) or carboplatin (23 patients) infusion was administered at a dose of 10 mg/M2/day or 30 mg/M2/day, respectively, day 7 to 14 and 35 to 42. Cycles were planned to be repeated consecutively in the absence of toxicity in patients with stable or responding disease. Sixteen patients also received etoposide 30 mg/M2/day as an admixture concomitant with administration of the platinum analogue. Therefore, the distribution of therapies was PLF 19, CLF 8, PLEF 14, and CLEF 2. RESULTS: A total of 63 courses of PLF +/- E was administered as outlined above. Hematologic toxicity was minimal with or without the addition of etoposide. Sixteen percent of patients developed an elevated creatinine with a median of 1.6 and a range of 1.6 to 3.2 mg %. Tumor responses were observed in seven of fourteen evaluable patients with squamous cell carcinoma of the lung (all of whom received concomitant etoposide). In addition, one patient with metastatic gallbladder cancer achieved a complete clinical response. CONCLUSION: Ambulatory infusional PLF with carboplatin or cisplatin using sequentially alternating delivery of the component antineoplastic agents is feasible and active with minimal toxicity. The addition of infusional etoposide to the PLF regimen does not substantially increase hematologic toxicity. Extended phase II studies in aerodigestive cancers are ongoing and a phase III trial comparing this ambulatory regimen to short-term PLF infusion (5-day) may be justified to compare the relative cost and benefits of the two schedules.
Adult↗
Multi-day fractionated administration schedule for paclitaxel.
PURPOSE: To establish the feasibility of fractionating paclitaxel administration by utilizing daily one-hour infusions for three, four or five days with dose escalating to determine the patterns of hematologic and non hematologic toxicities. PATTERNS AND METHODS: Forty patients received 87 courses of daily fractionated paclitaxel for three, four or five days; cycles were repeated every 21 days. Six patients received concomitant daily cisplatin. The median number of cycles delivered per patient was two with a range of one to six. RESULTS: Cumulative doses per cycle ranged from 120 mg/m2 to 250 mg/m2 with 25% of the cycles delivering 200 mg/m2 or more. Ten cycles (11.5%) were associated with dose limiting neutropenia (grade 3 [7 cycles]; grade 4 [3 cycles]). No hypersensitivity reactions were observed and no patient required cytokine support. No patient required hospitalization. CONCLUSIONS: Administering paclitaxel on a daily fractioned schedule in an ambulatory setting is logistically feasible; does not require premedication; is associated with a toxicity pattern similar to single day schedules (e.g. 24-hour or three-hour infusion); is capable of delivering a higher dose per cycle than published 96- or 120-hour infusion schedules; and could possibly be escalated to doses higher than 250 mg/m2 in carefully selected patients. The optimal dose rate for five-day multifractionated administration of paclitaxel is 40 to 50 mg/m2/d or a cumulative cycle dose of 200 to 250 mg/m2 and does not require cytokine usage. Adding cisplatin on a fractionated daily schedule may accentuate the neurotoxicity associated with both agents. A prospective comparison of four-day fractionated vs. four-day continuous infusional paclitaxel has been proposed as a randomized study to determine clinical differences in response, dose intensity and toxicity.
Antineoplastic Agents, Phytogenic↗
Second locus for Hirschsprung disease/Waardenburg syndrome in a large Mennonite kindred.
We have studied a large Mennonite kindred in which 20 members were affected with Hirschsprung disease (HSCR), 5 of whom had one or more manifestations of Waardenburg syndrome (WS) type II (WS2). Eleven additional relatives had signs of WS2 without HSCR. Since HSCR and WS2 each represent perturbations of neural crest migration/differentiation, this large pedigree with apparent cosegregation of HSCR and WS2 offered an opportunity to search for linkage between these loci, candidate genes, and random DNA markers, particularly in view of recent discoveries of genes for Waardenburg syndrome type I (WS1) and Hirschsprung disease (c-ret). We have examined the following possible linked markers in 69 relatives in this family: the c-ret gene (HSCR); the human PAX3 gene (HuP2) on chromosome 2q (WS1) and placental alkaline phosphatase (ALPP) on chromosome 2q (linked to WS1); argininosuccinate synthetase (ASS) on chromosome 9q, close to ABO blood groups which have shown weak linkage to WS; and the beta 1 GABA receptor gene (GABARB1) on chromosome 4q13-11, close to c-kit, deletions of which cause piebaldism. Linkage between any of these loci and HSCR/WS in this kindred was excluded, demonstrating that there is at least one further locus for HSCR other than c-ret.
Christianity↗
Mutations of the RET proto-oncogene in Hirschsprung's disease.
Hirschsprung's disease (HSCR) is a common condition (1 in 5,000 live births) resulting in intestinal obstruction in neonates and megacolon in infants and adults. This disease has been ascribed to the absence of autonomic ganglion cells, which are derived from the neural crest, in the terminal hindgut. Segregation analyses have suggested incompletely penetrant dominant inheritance in familial HSCR. Recently, a gene for HSCR has been mapped to chromosome 10q11.2 (refs 6, 7). No recombination was observed between the disease locus and the locus for the RET proto-oncogene, a protein tyrosine kinase gene expressed in the cells derived from the neural crest. Here we report nonsense and missense mutations in the extracellular domain of RET protein (exons 2, 3, 5 and 6) in six unrelated probands and show that the mutant genotypes segregate with the disease in HSCR families. Mutations of RET have been previously reported in multiple endocrine neoplasia type 2A (MEN 2A). Thus, germ-line mutations of the RET gene may contribute either to developmental anomalies in HSCR or to inherited predisposition to cancer in MEN 2A.
Base Sequence↗
Genetic analysis of glucokinase and the chromosome 20 diabetes susceptibility locus in families with type 2 diabetes.
Mutations of the glucokinase gene (chromosome 7p) have been shown to cause some cases of familial maturity onset diabetes of youth (MODY) but few, if any, cases of late onset familial Type 2 diabetes. A further single large pedigree with MODY has shown linkage to a marker for the adenosine deaminase gene (ADA, chromosome 20q), although the diabetes susceptibility gene at this locus has not been identified. We have studied members of 19 families with familial Type 2 diabetes (including 10 European families, 6 families from the Indian subcontinent, and 3 families of Afro-Caribbean origin), 2 of which were of MODY type (and both European), with a glucokinase marker and a marker linked to ADA, to examine whether glucokinase, or the unknown defect on chromosome 20, are implicated in diabetes in our pedigrees. Several models were constructed for standard two-point linkage analysis. Glucokinase is not the cause of diabetes in all of these families but was excluded in only one MODY family. It was possible to exclude both loci in the second MODY pedigree. No evidence was found of linkage to either marker in this multi-ethnic population under the models used. At least one further locus is involved in determining susceptibility to MODY.
Adult↗
Long segment and short segment familial Hirschsprung's disease: variable clinical expression at the RET locus.
Hirschsprung's disease (aganglionic megacolon, HSCR) is a frequent condition of unknown origin (1/5000 live births) resulting in intestinal obstruction in neonates and severe constipation in infants and adults. In the majority of cases (80%), the aganglionic tract involves the rectum and the sigmoid colon only (short segment HSCR), while in 20% of cases it extends toward the proximal end of the colon (long segment HSCR). In a previous study, we mapped a gene for long segment familial HSCR to the proximal long arm of chromosome 10 (10q11.2). Further linkage analyses in familial HSCR have suggested tight linkage of the disease gene to the RET protoncogene mapped to chromosome 10q11.2. Recently, nonsense and missense mutations of RET have been identified in HSCR patients. However, the question of whether mutations of the RET gene account for both long segment and short segment familial HSCR remained unanswered. We have performed genetic linkage analyses in 11 long segment HSCR families and eight short segment HSCR families using microsatellite DNA markers of chromosome 10q. In both anatomical forms, tight pairwise linkage with no recombinant events was observed between the RET proto-oncogene locus and the disease locus (Zmax = 2.16 and Zmax = 5.38 for short segment and long segment HSCR respectively at 0 = 0%) Multipoint linkage analyses performed in the two groups showed that the maximum likelihood estimate was at the RET locus. Moreover, we show that point mutations of the RET proto-oncogene occur either in long segment or in short segment HSCR families and we provide evidence for incomplete penetrance of the disease causing mutation. These data suggest that the two anatomical forms of familial HSCR, which have been separated on the basis of clinical and genetic criteria, may be regarded as the variable clinical expression of mutations at the RET locus.
Chromosome Mapping↗
[Mutations of RET proto-oncogene in Hirschsprung disease].
Hirschsprung's disease (HSCR) is a common condition (1 in 5,000 live births) resulting in intestinal obstruction in neonates and megacolon in infants and adults. This disease has been ascribed to the absence of autonomic ganglion cells, which are derived from the neural crest, in the terminal hindgut. Segregation analyses have suggested incompletely penetrant dominant inheritance in familial HSCR. Recently, a gene for HSCR has been mapped to chromosome 10q11.2. No recombination was observed between the disease locus and the locus for the RET proto-oncogene, a protein tyrosine kinase gene expressed in the cells derived from the neural crest. Here we report on nonsense and missense mutations in the extracellular domain of the RET protein (exons 2, 3, 5 and 6) in 6 unrelated probands and show that the mutant genotypes segregate with the disease in HSCR families. Mutations of RET have been previously reported in multiple endocrine neoplasia type 2A (MEN 2A). Thus, germ-line mutations of the RET gene may contribute either to developmental anomalies in HSCR or to inherited predisposition to cancer in MEN 2A.
Codon, Nonsense↗