Genetic Counseling and Genetic Testing for Familial Hypercholesterolemia.

Familial hypercholesterolemia (FH) is one of the most common autosomal codominant Mendelian diseases. The major complications of FH include tendon and cutaneous xanthomas and coronary artery disease (CAD) associated with a substantial elevation of serum low-density lipoprotein levels (LDL). Genetic counseling and genetic testing for FH is useful for its diagnosis, risk stratification, and motivation for further LDL-lowering treatments. In this study, we summarize the epidemiology of FH based on numerous genetic studies, including its pathogenic variants, genotype-phenotype correlation, prognostic factors, screening, and usefulness of genetic counseling and genetic testing. Due to the variety of treatments available for this common Mendelian disease, genetic counseling and genetic testing for FH should be implemented in daily clinical practice.

Real-world safety and effectiveness of ledipasvir/sofosbuvir for the treatment of chronic hepatitis C virus genotype 1 in Japan.

As patients with chronic hepatitis C virus (HCV) tend to be older and/or have advanced liver disease in Japan, real-world data are needed to evaluate safe and effective treatment options. The study aim was to assess safety and effectiveness of ledipasvir/sofosbuvir (LDV/SOF) in a real-world cohort of Japanese patients with HCV genotype (GT) 1 infection overall and by patient subgroups: elderly, compensated cirrhotic, advanced fibrotic and those with hepatocellular carcinoma (HCC). A large prospective observational study was conducted, enrolling adult patients treated for HCV GT1 infection with LDV/SOF at clinical sites across Japan. Patients were observed for safety outcomes during and 4 weeks after treatment, and for sustained virologic response at 12-weeks post-treatment (SVR12). Incidence rates (IRs) of adverse drug reactions (ADRs) and serious ADRs (SADRs) and SVR12 rates were assessed overall and by subgroups. ADR and SADR IRs were low (2.26 and 0.17 per 100 person-months, respectively) and did not significantly differ in elderly patients or those with presence of compensated cirrhosis, worsening fibrosis or HCC. SVR12 rates were high overall (98.5%) and across subgroups investigated (≥94%), including patients who were elderly (98.2%), treatment-experienced (97.6%), advanced fibrotic (≥95.8%), had existing NS5A resistance-associated substitutions reported pre-treatment (95.0%), compensated cirrhosis (95.7%), HCC (94.0%) and other chronic liver diseases (96.1%). In this large, real-world observational study of Japanese patients with HCV GT1 infection, LDV/SOF treatment resulted in low incidence of adverse events, with high real-world effectiveness, even among patients with potentially higher risks of adverse safety outcomes and treatment failure.

Germline mutation landscape of multiple endocrine neoplasia type 1 using full gene next-generation sequencing.

Background Loss-of-function germline MEN1 gene mutations account for 75-95% of patients with multiple endocrine neoplasia type 1 (MEN1). It has been postulated that mutations in non-coding regions of MEN1 might occur in some of the remaining patients; however, this hypothesis has not yet been fully investigated. Objective To sequence for the entire MEN1 including promoter, exons and introns in a large MEN1 cohort and determine the mutation profile. Methods and patients A target next-generation sequencing (tNGS) assay comprising 7.2 kb of the full MEN1 was developed to investigate germline mutations in 76 unrelated MEN1 probands (49 familial, 27 sporadic). tNGS results were validated by Sanger sequencing (SS), and multiplex ligation-dependent probe amplification (MLPA) assay was applied when no mutations were identifiable by both tNGS and SS. Results Germline MEN1 variants were verified in coding region and splicing sites of 57/76 patients (74%) by both tNGS and SS (100% reproducibility). Thirty-eight different pathogenic or likely pathogenic variants were identified, including 13 new and six recurrent variants. Three large deletions were detected by MLPA only. No mutation was detected in 16 patients. In untranslated, regulatory or in deep intronic MEN1 regions of the 76 MEN1 cases, no point or short indel pathogenic variants were found in untranslated, although 33 benign/likely benign and three new VUS variants were detected. Conclusions Our study documents that point or short indel mutations in non-coding regions of MEN1 are very rare events. Also, tNGS proved to be a highly effective technology for routine genetic MEN1 testing.

Penetrance and clinical features of pheochromocytoma in a six-generation family carrying a germline TMEM127 mutation.

CONTEXT: The phenotype of familial pheochromocytoma (PHEO) associated with germline TMEM127 mutations (TMEM127-related PHEO) has not been clearly defined. OBJECTIVE: This study aimed to investigate the penetrance, full phenotypic spectrum and effectiveness of clinical/genetic screening in TMEM127-related PHEO. DESIGN, SETTING, AND PARTICIPANTS: Clinical and genetic screening, and genetic counseling were offered to 151 individuals from a six-generation family carrying a TMEM127 germline mutation in a referral center. INTERVENTION AND MAIN OUTCOME MEASURES: TMEM127 genetic testing was offered to at-risk relatives and clinical surveillance for pheochromocytoma was performed in mutation-positive carriers. RESULTS: Forty seven individuals carried the c.410-2A>C TMEM127 mutation. Clinical data were obtained from 34 TMEM127-mutation carriers followed up for 8.7 ± 8.1 years (range, 1-20 y). Pheochromocytoma was diagnosed in 11 carriers (32%) at a median age of 43 years. In nine patients, symptoms started at 29 years (range, 10-55 y) and two cases were asymptomatic. Tumors were multicentric in five (45%) and bilateral in five (45%) patients. Six patients (54%) had at least one adrenomedullary nodule less than 10 mm. No paragangliomas, distant metastases, or other manifestations were detected. Cumulative penetrance of pheochromocytoma was 0% at 0-20 years, 3% at 21-30 years, 15% at 31-40 years, 24% at 41-50 years, and 32% at 51-65 years. The youngest case was diagnosed at 22 years and the earliest symptoms were reported at age 10. CONCLUSIONS: Tumor multicentricity, nodular adrenomedullary hyperplasia, and the occurrence of symptoms more than a decade earlier than the age at diagnosis are novel findings in TMEM127-related PHEO. The high penetrance of pheochromocytoma in this condition validates the benefits of genetic testing of at-risk relatives. We thus recommend that TMEM127 genetic testing should be offered to at-risk individuals at age 22 years and mutation carriers should undergo clinical surveillance annually.

Comprehensive assessment of the disputed RET Y791F variant shows no association with medullary thyroid carcinoma susceptibility.

Accurate interpretation of germline mutations of the rearranged during transfection (RET) proto-oncogene is vital for the proper recommendation of preventive thyroidectomy in medullary thyroid carcinoma (MTC)-prone carriers. To gain information regarding the most disputed variant of RET, ATA-A Y791F, we sequenced blood DNA samples from a cohort of 2904 cancer-free elderly individuals (1261 via Sanger sequencing and 1643 via whole-exome/genome sequencing). We also accessed the exome sequences of an additional 8069 individuals from non-cancer-related laboratories and public databanks as well as genetic results from the Catalogue of Somatic Mutations in Cancer (COSMIC) project. The mean allelic frequency observed in the controls was 0.0031, with higher occurrences in Central European populations (0.006/0.008). The prevalence of RET Y791F in the control databases was extremely high compared with the 40 known RET pathogenic mutations (P=0.00003), while no somatic occurrence has been reported in tumours. In this study, we report new, unrelated Brazilian individuals with germline RET Y791F-only: two tumour-free elderly controls; two individuals with sporadic MTC whose Y791F-carrying relatives did not show any evidence of tumours; and a 74-year-old phaeochromocytoma patient without MTC. Furthermore, we showed that the co-occurrence of Y791F with the strong RET C634Y mutation explains the aggressive MTC phenotypes observed in a large affected family that was initially reported as Y791F-only. Our literature review revealed that limited analyses have led to the misclassification of RET Y791F as a probable pathogenic variant and, consequently, to the occurrence of unnecessary thyroidectomies. The current study will have a substantial clinical influence, as it reveals, in a comprehensive manner, that RET Y791F only shows no association with MTC susceptibility.

Association between the p27 rs2066827 variant and tumor multiplicity in patients harboring MEN1 germline mutations.

OBJECTIVE: To date, no evidence of robust genotype-phenotype correlation or disease modifiers for multiple endocrine neoplasia type 1 (MEN1) syndrome has been described, leaving the highly variable clinical presentation of patients unaccounted for. DESIGN: As the CDKN1B (p27) gene causes MEN4 syndrome and it is transcriptionally regulated by the product of the MEN1 gene (menin), we sought to analyze whether p27 influences the phenotype of MEN1-mutated patients. The cohort consisted of 100 patients carrying germline MEN1 gene mutations and 855 population-matched control individuals. METHODS: Genotyping of the coding p27 c.326T>G (V109G) variant was performed by sequencing and restriction site digestion, and the genotypes were associated with clinical parameters by calculating odds ratios (ORs) and their 95% CIs using logistic regression. RESULTS: There were significant differences in p27 V109G allele frequencies between controls and MEN1-mutated patients (OR=2.55, P=0.019, CI=1.013-5.76). Among patients who are ≥30 years old carrying truncating MEN1 mutations, the T allele was strongly associated with susceptibility to tumors in multiple glands (three to four glands affected vs one to two glands affected; OR=18.33; P=0.002, CI=2.88-16.41). This finding remained significant after the Bonferroni's multiple testing correction, indicating a robust association. No correlations were observed with the development of MEN1-related tumors such as hyperparathyroidism, pituitary adenomas, and enteropancreatic and adrenocortical tumors. CONCLUSIONS: Our study suggests that the p27 tumor suppressor gene acts as a disease modifier for the MEN1 syndrome associated with MEN1 germline mutations. If confirmed in independent patient cohorts, this finding could facilitate the management of this clinically complex disease.

p27 variant and corticotropinoma susceptibility: a genetic and in vitro study.

Germline mutations in p27(kip1) are associated with increased susceptibility to multiple endocrine neoplasias (MEN) both in rats and humans; however, the potential role of common polymorphisms of this gene in endocrine tumor susceptibility and tumorigenesis remains mostly unrecognized. To assess the risk associated with polymorphism rs2066827 (p27-V109G), we genotyped a large cohort of Brazilian patients with sporadic endocrine tumors (pituitary adenomas, n=252; pheochromocytomas, n=125; medullary thyroid carcinoma, n=51; and parathyroid adenomas, n=19) and 885 population-matched healthy controls and determined the odds ratios and 95% CIs. Significant associations were found for the group of patients with pituitary adenomas (P=0.01), particularly for those with ACTH-secreting pituitary adenomas (P=0.005). In contrast, no association was found with GH-secreting pituitary tumors alone or with the sporadic counterpart of MEN2-component neoplasias. Our in vitro analyses revealed increased colony formation and cell growth rate for an AtT20 corticotropin mouse cell line overexpressing the p27-V109G variant compared with cells transfected with the WT p27. However, the genotypic effects in genetic and in vitro approaches were divergent. In accordance with our genetic data showing specificity for ACTH-secreting pituitary tissues, the overexpression of p27-V109G in a GH3 somatotropin rat cell line resulted in no difference compared with the WT. Pituitary tumors are one of the major clinical components of syndromes associated with the p27 pathogenic mutations MENX and MEN4. Our genetic and in vitro data indicate that the common polymorphism rs2066827 may play a role in corticotropinoma susceptibility and tumorigenesis through a molecular mechanism not fully understood thus far.

Penetrance of functioning and nonfunctioning pancreatic neuroendocrine tumors in multiple endocrine neoplasia type 1 in the second decade of life.

CONTEXT: Data are scarce on the penetrance of multiple endocrine neoplasia type 1 (MEN1)-related nonfunctioning pancreatic neuroendocrine tumors (NF-PETs) and insulinomas in young MEN1 patients. A potential positive correlation between tumor size and malignancy (2-3 cm, 18%; >3 cm, 43%) has greatly influenced the management of MEN1 adults with NF-PETs. OBJECTIVE: The aim of the study was to estimate the penetrance of NF-PETs, insulinomas, and gastrinomas in young MEN1 carriers. DESIGN: The data were obtained from a screening program (1996-2012) involving 113 MEN1 patients in a tertiary academic reference center. PATIENTS: Nineteen MEN1 patients (aged 12-20 y; 16 patients aged 15-20 y and 3 patients aged 12-14 y) were screened for NF-PETs, insulinomas, and gastrinomas. METHODS: Magnetic resonance imaging/computed tomography and endoscopic ultrasound (EUS) were performed on 10 MEN1 carriers, magnetic resonance imaging/computed tomography was performed on five patients, and four other patients underwent an EUS. RESULTS: The overall penetrance of PETs during the second decade of life was 42% (8 of 19). All eight PET patients had NF-PETs, and half of those tumors were multicentric. One-fifth of the screened patients (21%; 4 of 19) harbored at least one large tumor (>2.0 cm). Insulinoma was detected in two NF-PET patients (11%) at the initial screening; gastrinoma was not present in any cases. Six of the 11 (54%) screened patients aged 15-20 years who underwent an EUS had NF-PETs. Potential false-positive EUS results were excluded based on EUS-guided biopsy results, the reproducibility of the NF-PET findings, or the observation of increased tumor size during follow-up. Distal pancreatectomy and the nodule enucleation of pancreatic head tumors were conducted on three patients with large tumors (>2.0 cm; T2N0M0) that were classified as grade 1 neuroendocrine tumors (Ki-67<2%). CONCLUSIONS: Our data demonstrated high penetrance of NF-PETs in 15- to 20-year-old MEN1 patients. The high percentage of the patients presenting consensus criteria for surgery for NF-PET alone or NF-PET/insulinoma suggests a potential benefit for the periodic surveillance of these tumors in this age group.

Polymorphisms in the p27kip-1 and prohibitin genes denote novel genes associated with melanoma risk in Brazil, a high ultraviolet index region.

Ultraviolet (UV) radiation is a major environmental risk factor to the development of cutaneous melanoma as it induces pyrimidine dimers in DNA. Genes that exert their function by arresting the cell cycle are critical to avoid carcinogenic mutations, allowing the processing of DNA repair systems. This study was carried out to evaluate the role of polymorphisms in cell cycle genes such as TP53, p27, CDKN2A, prohibitin, and GADD153 in melanoma risk as well as their influence on known risk factors in a high UV index region. A hospital-based case-control study was carried out in Brazil to evaluate the contribution of polymorphisms in cell cycle genes toward melanoma risk. The study comprised 202 melanoma patients and 210 controls. The polymorphisms analyzed were TP53 Arg72Pro, p27 Val109Gly, GADD153 Phe10Phe (rs697221), CDKN2A 3'UTR C540G, and prohibitin 3'UTR C1703T. As regards, p27 Val109Gly, both heterozygous and homozygous Gly genotypes were shown to be protective genotypes on calculating both crude and adjusted odds ratios (ORs) for age, sex, and educational level [OR 0.37; 95% confidence interval (CI) 0.16-0.87; P<0.05]. Similarly, the prohibitin TT genotype increased melanoma risk in the crude and adjusted analyses (OR 2.40; 95% CI 1.10-5.26; P<0.05). The p27 Gly protective genotype decreased the risk for melanoma in a stratified analysis of the known risk factors such as hair and eye color, sunburns, pigmented lesions, and European ancestry. The prohibitin TT genotype increased the risk of melanoma by such host factors. Our results showed for the first time that polymorphisms in p27 Val109Gly and in prohibitin 3'UTR C1703T genotypes modulate the risk to melanoma in a high UV index region.

Análise do gene CDKN1B/p27kip1 em pacientes com neoplasia endócrina múltipla tipo 2 / CDKN1B/p27kip1 gene analysis in patients with multiple endolcrine neopasia type 2 (MEN2)

INTRODUÇÃO: Na Neoplasia Endócrina Múltipla tipo 2 (NEM2), o desenvolvimento do Carcinoma Medular de Tireoide (CMT), Feocromocitoma (FEO) e Hiperparatireoidismo primário (HPT) está associado à mutações germinativas ativadoras no proto-oncogene RET. Casos de CMT esporádico podem apresentar mutações somáticas no RET (~40%). A variabilidade fenotípica observada em casos de CMT e FEO familiais associados à NEM2 indica o envolvimento de eventos genéticos adicionais que seriam responsáveis pelas diferenças clínicas observadas nos indivíduos afetados (idade de desenvolvimento, progressão e agressividade do tumor). Outras alterações genéticas no RET como duplas mutações, SNPs e haplótipos específicos podem influenciar na susceptibilidade, agressividade e modulação do fenótipo NEM2. Entretanto, os estudos de outros genes envolvidos no processo da tumorigênese NEM2 ainda estão em andamento. Recentemente foi mostrado que RET ativado controla a expressão de proteínas inibidoras do ciclo celular (p18 e p27). Mutações germinativas no gene p27 foram recentemente associadas à susceptibilidade de tumores neuroendócrinos e estão associadas à síndrome NEM4 (Neoplasia endócrina múltipla tipo 4). Mutações somáticas, inativadoras de p27, são raramente encontradas em vários tipos de tumores. Entretanto, diversos estudos documentaram que a redução na expressão e a sublocalização citoplamática de p27 são controladas por alterações pós-transducionais e/ou epigenéticas. OBJETIVOS: o estudo teve como objetivos avaliar a participação de genes, recentemente associados ao RET ativado, em tumores de pacientes com NEM2 e também verificar se polimorfismos no gene p27 estariam atuando como moduladores de fenótipo em uma grande família com NEM2. CASUÍTICA: foram analisadas 66 amostras tumorais advindas de 36 pacientes com diagnóstico clínico e genético de NEM2 e 28 indivíduos pertencentes a uma grande família com NEM2A-CMTF e mutação C620R no gene RET. MÉTODOS:...

INTRODUCTION: In Multiple Endocrine Neoplasia type 2 (MEN2) the development of medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO) and primary hyperparathyroidism (HPT) are associated with activating germline mutations in RET proto-oncogene. Cases of sporadic MTC may have somatic RET mutations (~ 40%). The phenotypic variability observed in cases with familial MTC/MEN2 and PHEO/MEN2 indicates the probable involvement of additional genetic events that could be responsible for the clinical differences observed in the affected individuals (age development, progression and aggressiveness of the tumor). Other genetic alterations such as RET double mutations, SNPs and specific haplotypes may influence susceptibility, aggressiveness and MEN2 phenotype modulation. However, studies of other genes involved in the tumorigenesis of MEN2 are still in progress. Recently, it was shown that the activated RET controls the expression of cell cycle inhibitory proteins (p18 and p27). Germline mutations in the p27 gene have recently been associated with the susceptibility to neuroendocrine tumors and are associated with the MEN4 syndrome (Multiple endocrine neoplasia type 4). Somatic inactivating mutations p27 are rarely found in many types of tumors. However, several studies have documented that reduced expression and subcellular location of p27 is controlled by post-transductional changes and/or epigenetic factors. OBJECTIVES: This study aimed to evaluate the role of genes recently associated with RET activated in tumors from MEN2 patients and also check whether polymorphisms in the p27 gene would be acting as modulators of phenotype in a large MEN2 family. PATIENTS: We analyzed 66 tumor samples from 36 patients with clinical and genetic diagnosis of MEN2 and from 28 individuals belonging to a large family with FMTC/MEN2A and RET C620R mutation. METHODS: The analyses of somatic p27, p15, p18 and RET...

Narrowing the gap of personalized medicine in emerging countries: the case of multiple endocrine neoplasias in Brazil.

The finished version of the human genome sequence was completed in 2003, and this event initiated a revolution in medical practice, which is usually referred to as the age of genomic or personalized medicine. Genomic medicine aims to be predictive, personalized, preventive, and also participative (4Ps). It offers a new approach to several pathological conditions, although its impact so far has been more evident in mendelian diseases. This article briefly reviews the potential advantages of this approach, and also some issues that may arise in the attempt to apply the accumulated knowledge from genomic medicine to clinical practice in emerging countries. The advantages of applying genomic medicine into clinical practice are obvious, enabling prediction, prevention, and early diagnosis and treatment of several genetic disorders. However, there are also some issues, such as those related to: (a) the need for approval of a law equivalent to the Genetic Information Nondiscrimination Act, which was approved in 2008 in the USA; (b) the need for private and public funding for genetics and genomics; (c) the need for development of innovative healthcare systems that may substantially cut costs (e.g. costs of periodic medical followup); (d) the need for new graduate and postgraduate curricula in which genomic medicine is emphasized; and (e) the need to adequately inform the population and possible consumers of genetic testing, with reference to the basic aspects of genomic medicine.

RET haplotype, not linked to the C620R activating mutation, associated with Hirschsprung disease in a novel MEN2 family.

Hirschsprung disease is a congenital form of aganglionic megacolon that results from cristopathy. Hirschsprung disease usually occurs as a sporadic disease, although it may be associated with several inherited conditions, such as multiple endocrine neoplasia type 2. The rearranged during transfection (RET) proto-oncogene is the major susceptibility gene for Hirschsprung disease, and germline mutations in RET have been reported in up to 50% of the inherited forms of Hirschsprung disease and in 15-20% of sporadic cases of Hirschsprung disease. The prevalence of Hirschsprung disease in multiple endocrine neoplasia type 2 cases was recently determined to be 7.5% and the cooccurrence of Hirschsprung disease and multiple endocrine neoplasia type 2 has been reported in at least 22 families so far. It was initially thought that Hirschsprung disease could be due to disturbances in apoptosis or due to a tendency of the mutated RET receptor to be retained in the Golgi apparatus. Presently, there is strong evidence favoring the hypothesis that specific inactivating haplotypes play a key role in the fetal development of congenital megacolon/Hirschsprung disease. In the present study, we report the genetic findings in a novel family with multiple endocrine neoplasia type 2: a specific RET haplotype was documented in patients with Hirschsprung disease associated with medullary thyroid carcinoma, but it was absent in patients with only medullary thyroid carcinoma. Despite the limited number of cases, the present data favor the hypothesis that specific haplotypes not linked to RET germline mutations are the genetic causes of Hirschsprung disease.

Somatotroph pituitary adenoma with acromegaly and autosomal dominant polycystic kidney disease: SSTR5 polymorphism and PKD1 mutation.

A 39-year-old woman with autosomal dominant polycystic kidney disease (ADPKD) presented with acromegaly and a pituitary macroadenoma. There was a family history of this renal disorder. She had undergone surgery for pituitary adenoma 6 years prior. Physical examination disclosed bitemporal hemianopsia and elevation of both basal growth hormone (GH) 106 ng/mL (normal 0-5) and insulin-like growth factor (IGF-1) 811 ng/mL (normal 48-255) blood levels. A magnetic resonance imaging scan disclosed a 3.0 cm sellar and suprasellar mass with both optic chiasm compression and left cavernous sinus invasion. Pathologic, cytogenetic, molecular and in silico analysis was undertaken. Histologic, immunohistochemical and ultrastructural studies of the lesion disclosed a sparsely granulated somatotroph adenoma. Standard chromosome analysis on the blood sample showed no abnormality. Sequence analysis of the coding regions of PKD1 and PKD2 employing DNA from both peripheral leukocytes and the tumor revealed the most common PKD1 mutation, 5014_5015delAG. Analysis of the entire SSTR5 gene disclosed the variant c.142C>A (p.L48M, rs4988483) in the heterozygous state in both blood and tumor, while no pathogenic mutations were noted in the MEN1, AIP, p27Kip1 and SSTR2 genes. To our knowledge, this is the fourth reported case of a GH-producing pituitary adenoma associated with ADPKD, but the first subjected to extensive morphological, ultrastructural, cytogenetic and molecular studies. The physical proximity of the PKD1 and SSTR5 genes on chromosome 16 suggests a causal relationship between ADPKD and somatotroph adenoma.

Narrowing the gap of personalized medicine in emerging countries: the case of multiple endocrine neoplasias in Brazil

The finished version of the human genome sequence was completed in 2003, and this event initiated a revolution in medical practice, which is usually referred to as the age of genomic or personalized medicine. Genomic medicine aims to be predictive, personalized, preventive, and also participative (4Ps). It offers a new approach to several pathological conditions, although its impact so far has been more evident in mendelian diseases. This article briefly reviews the potential advantages of this approach, and also some issues that may arise in the attempt to apply the accumulated knowledge from genomic medicine to clinical practice in emerging countries. The advantages of applying genomic medicine into clinical practice are obvious, enabling prediction, prevention, and early diagnosis and treatment of several genetic disorders. However, there are also some issues, such as those related to: (a) the need for approval of a law equivalent to the Genetic Information Nondiscrimination Act, which was approved in 2008 in the USA; (b) the need for private and public funding for genetics and genomics; (c) the need for development of innovative healthcare systems that may substantially cut costs (e.g. costs of periodic medical followup); (d) the need for new graduate and postgraduate curricula in which genomic medicine is emphasized; and (e) the need to adequately inform the population and possible consumers of genetic testing, with reference to the basic aspects of genomic medicine.

RET haplotype, not linked to the C620R activating mutation, associated with Hirschsprung disease in a novel MEN2 family

Hirschsprung disease is a congenital form of aganglionic megacolon that results from cristopathy. Hirschsprung disease usually occurs as a sporadic disease, although it may be associated with several inherited conditions, such as multiple endocrine neoplasia type 2. The rearranged during transfection (RET) proto-oncogene is the major susceptibility gene for Hirschsprung disease, and germline mutations in RET have been reported in up to 50% of the inherited forms of Hirschsprung disease and in 15-20% of sporadic cases of Hirschsprung disease. The prevalence of Hirschsprung disease in multiple endocrine neoplasia type 2 cases was recently determined to be 7.5% and the cooccurrence of Hirschsprung disease and multiple endocrine neoplasia type 2 has been reported in at least 22 families so far. It was initially thought that Hirschsprung disease could be due to disturbances in apoptosis or due to a tendency of the mutated RET receptor to be retained in the Golgi apparatus. Presently, there is strong evidence favoring the hypothesis that specific inactivating haplotypes play a key role in the fetal development of congenital megacolon/Hirschsprung disease. In the present study, we report the genetic findings in a novel family with multiple endocrine neoplasia type 2: a specific RET haplotype was documented in patients with Hirschsprung disease associated with medullary thyroid carcinoma, but it was absent in patients with only medullary thyroid carcinoma. Despite the limited number of cases, the present data favor the hypothesis that specific haplotypes not linked to RET germline mutations are the genetic causes of Hirschsprung disease.