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Rare diseases pose specific challenges in the field of medical research to provide physicians with evidence based guidelines derived from studies with sufficient quality. An example of these rare diseases is multiple endocrine neoplasia type 1 (MEN1), which is an autosomal dominant endocrine tumor syndrome with an estimated occurrence rate of 2-3 per 100.000. For this complex disease, characterized by multiple endocrine tumors, it proves difficult to perform both adequate and feasible studies. The opinion of patients themselves is of utmost importance to identify the gaps in the evidence based medicine regarding clinical care. In the search for scientific answers to clinical research questions, the aim for best available evidence is obvious. Observational studies within patient cohorts, although prone to bias, seem the most feasible study design regarding the disease prevalence. Knowledge and adaptation to all types of bias is demanded in the strive for answers. Guided by our research on MEN1 patients, we elaborate on strategies to identify sufficient patients, to maximize and maintain patient enrollment and to standardize the data collection process. Preferably, data collection is performed prospectively, however, under certain conditions data storage in a longitudinal retrospective database with a disease-specific framework is suitable. Considering the global challenges on observational research on rare diseases, we propose a stepwise approach from clinical research questions to scientific answers.

Background: Multiple Endocrine Neoplasia type 1 (MEN1) is diagnosed when two out of the three primary MEN1-associated endocrine tumors occur in a patient. Up to 10-30 % of those patients have no mutation in the MEN1 gene. It is unclear if the phenotype and course of the disease of mutation-negative patients is comparable with mutation-positive patients and if these patients have true MEN1. The present study aims to describe and compare the clinical course of MEN1 mutation-negative patients with two out of the three main MEN1 manifestations and mutation-positive patients during long-term follow-up., Methods: This is a cohort study performed using the Dutch MEN1 database, including > 90 % of the Dutch MEN1 population., Results: A total of 293 (90.7 %) mutation-positive and 30 (9.3 %) mutation-negative MEN1 patients were included. Median age of developing the first main MEN1 manifestation was higher in mutation-negative patients (46 vs. 33 years) (P = 0.007). Mutation-negative patients did not develop a third main MEN1 manifestation in the course of follow-up compared to 48.3 % of mutation-positive patients (P < 0.001). Median survival in mutation-positive patients was estimated at 73.0 years (95 % CI, 69.5-76.5) compared to 87.0 years (95 % CI not available) in mutation-negative patients (P = 0.001)., Conclusions: Mutation-positive and mutation-negative MEN1 patients have a different phenotype and clinical course. Mutation-negative patients develop MEN1 manifestations at higher age and have a life expectancy comparable with the general population. The apparent differences in clinical course suggest that MEN1 mutation-negative patients do not have true MEN1, but another MEN1-like syndrome or sporadic co-incidence of two neuro-endocrine tumors.

Objective: Identifying a germline mutation in the multiple endocrine neoplasia type 1 (MEN1) gene in an index case has consequences for a whole family. Eligible family members should be offered genetic counseling and MEN1 mutation testing. Subsequently, clinical screening of mutation carriers according to the guidelines should be initiated. We assessed whether there is a lag time from MEN1 diagnosis of the index case to MEN1 diagnosis of family members. In addition, we determined whether this lag time was associated with an increased morbidity and mortality risk., Design: A cohort study was performed using the Dutch MEN1 database, including >90% of the Dutch MEN1 population >16 years of age (n = 393)., Results: Fifty-eight MEN1 families were identified, of whom 57 were index cases and 247 were non-index cases (n = 304). The median lag time in MEN1 diagnosis of family members was 3.5 (range, 0-30) years. At the time of MEN1 diagnosis, 30 (12.1%) non-index cases had a duodenopancreatic neuroendocrine tumor, of whom 20% had metastases with a mean lag time of 10.9 years, in comparison with 7.1 years without metastases. Twenty-five (10.1%) non-index cases had a pituitary tumor, of whom 80% had a microadenoma and 20% had a macroadenoma, with mean lag times of 7.2 and 10.6 years, respectively. Ninety-five (38.4%) non-index cases had a primary hyperparathyroidism with a mean lag time of 9.5 years in comparison with seven patients without a primary hyperparathyroidism with a mean lag time of 3 years (P = .005). Ten non-index cases died because of a MEN1-related cause that developed during or before the lag time., Conclusion: There is a clinically relevant delay in MEN1 diagnosis in families because of a lag time between the diagnosis of an index case and the rest of the family. More emphasis should be placed on the conduct of proper counseling and genetic testing in all eligible family members.

Context: An association between ABO blood type and the development of cancer, in particular, pancreatic cancer, has been reported in the literature. An association between blood type O and neuroendocrine tumors in multiple endocrine neoplasia type 1 (MEN1) patients was recently suggested. Therefore, blood type O was proposed as an additional factor to personalize screening criteria for neuroendocrine tumors in MEN1 patients., Objective: The aim of this study was to assess the association between blood type O and the occurrence of neuroendocrine tumors in the national Dutch MEN1 cohort., Design: This is a cohort study using the Dutch National MEN1 database, which includes more than 90% of the Dutch MEN1 population. Demographic and clinical data were analyzed by blood type. Chi-square tests and Fisher exact tests were used to determine the association between blood type O and occurrence of neuroendocrine tumors. A cumulative incidence analysis (Gray's test) was performed to assess the equality of cumulative incidence of neuroendocrine tumors in blood type groups, taking death into account as a competing risk., Results: The ABO blood type of 200 of 322 MEN1 patients was known. Demographic and clinical characteristics were similar among blood type O and non-O type cohorts. The occurrence of neuroendocrine tumors of the lung, thymus, pancreas, and gastrointestinal tract was equally distributed across the blood type O and non-O type cohorts (Grays's test for equality; P = 0.72). Furthermore, we found no association between blood type O and the occurrence of metastatic disease or survival., Conclusions: An association between blood type O and the occurrence of neuroendocrine tumors in MEN1 patients was not confirmed. For this reason, the addition of the blood type to screening and surveillance practice seems not to be of additional value for identifying MEN1 patients at risk for the development of neuroendocrine tumors, metastatic disease, or a shortened survival.

Context: Guidelines advise lifelong radiological followup for asymptomatic pituitary adenomas (PITs) because of the risk for growth and subsequent visual field defects. In the context of multiple endocrine neoplasia type 1 (MEN1) an even more comprehensive screening is advised because PITs are presumed to manifest more aggressive behavior. We studied the long-term course of MEN1-related PITs, which may be used as a model for sporadically occurring PITs., Objective: The aim of our study is to assess the results of systematic pre-symptomatic PIT screening and subsequent long-term followup of PITs with emphasis on nonfunctioning microadenomas diagnosed by screening., Patients and Methods: A cohort study was performed using the Dutch national MEN1 database, including greater than 90% of the Dutch MEN1 population older than 16 years (n = 323)., Main Outcome Measures: Screening results, natural course, and effects of treatment of PIT were assessed., Results: PIT was diagnosed in 123 patients with MEN1 (38.1 %), of whom 66 were diagnosed by MEN1-related screening. Ninety-one percent of the nonfunctioning PIT detected during screening (n = 35), did not require intervention during followup (median, 6.0 y). Three microadenomas showed limited growth but did not progress toward macroadenomas. Both screening-detected and prevalent prolactinomas (n = 52) responded well to treatment with dopamine agonists., Conclusion: Systematic presymptomatic screening for PIT in patients with MEN1 predominantly results in detection of nonfunctioning microadenomas. Prolactinoma in patients with MEN1 responded well to medical treatment. Microadenomas grew only occasionally and after many years without clinical consequences. Frequent magnetic resonance imaging followup of nonfunctioning microadenomas in the context of MEN1 and sporadically occurring PITs therefore seems debatable.

Objective: Currently, little is known about the prevalence of thyroid tumors in multiple endocrine neoplasia type 1 (MEN1) patients and it is unclear whether tumorigenesis of these thyroid tumors is MEN1-related. The aim of the study was to assess the prevalence of thyroid incidentalomas in MEN1 patients compared with nonMEN1 patients and to verify whether thyroid tumorigenesis is MEN1-related., Design: A cross-sectional study., Methods: The study included two groups: patients with MEN1 and a matched non-MEN1 control group without known thyroid disease, who underwent an ultrasound of the neck for the localization of parathyroid adenoma. Ninety-five MEN1 patients underwent ultrasound of the neck and were matched on gender and age with non-MEN1 patients. The prevalence of thyroid incidentalomas described in the ultrasound report was scored. Multinodular goiters, solitary nodes, and cysts were scored as incidentalomas. Presence of nuclear menin expression was evaluated by menin immunostaining of the thyroid tumors., Results: In the MEN1 group, 43 (45%) patients had a thyroid incidentaloma compared with 48 (51%) in the non-MEN1 group, of which 14 (15%) and 16 (17%), respectively, were solitary nodes. Menin was expressed in the nuclei of all evaluated thyroid tumors., Conclusions: MEN1 patients do not have a higher prevalence of thyroid incidentalomas compared with primary hyperparathyroidism patients without the diagnosis of MEN1. Menin was expressed in the thyroid tumors of MEN1 patients., (© 2015 European Society of Endocrinology.)

Context: The natural course and survival of neuroendocrine tumors (NETs) of thymus (Th) and lung in multiple endocrine neoplasia type 1 (MEN1) patients are still unknown., Objective: Our objective was to assess prevalence, tumor growth, and survival of Th and lung NETs in an unselected MEN1 population with long-term follow-up., Design: This was an observational study., Patients and Methods: A longitudinal study was performed using the Dutch national MEN1 database, including >90% of the Dutch MEN1 population >16 years of age. Patients under care of the Dutch University Medical Centers (1990-2011) (n = 323) were included., Main Outcome Measures: The prevalence and survival of Th and lung NETs were assessed. Linear mixed-models analysis was applied to assess tumor growth with age as a possible confounder and gender, genotype and baseline tumor size as possible effect modifiers., Results: Th NETs occurred in 3.4% of patients, almost exclusively in males with a 10-year survival of 25% (95% confidence interval = 8%-80%). A thoracic computed tomography scan was available in 188 patients (58.2%). A lung NET was identified in 42 patients (13.0%) with a 10-year survival of 71.1% (95% confidence interval = 51%-100%). Tumor volume of lung NETs increased 17% per year (P < .001) (tumor doubling time 4.5 years). Tumor doubling time in males was 2.5 vs 5.5 years in females (P = .05). Lung NET growth was not associated with genotype or with baseline tumor size (<1 vs ≥1 cm)., Conclusion: In MEN1 patients, Th NETs almost exclusively occurred in males and had a very low prevalence and a high mortality. Lung NETs occurred more often than previously thought, had an indolent course, and occurred equally in both sexes. Tumor growth in males was double compared with female patients.

Mutations of the multiple endocrine neoplasia type 1 (MEN1) gene lead to loss of function of its protein product menin. In keeping with its tumor suppressor function in endocrine tissues, the majority of the MEN1-related neuroendocrine tumors (NETs) show loss of heterozygosity (LOH) on chromosome 11q13. In sporadic NETs, MEN1 mutations and LOH are also reported, indicating common pathways in tumor development. Prevalence of thymic NETs (thNETs) and pulmonary carcinoids in MEN1 patients is 2-8%. Pulmonary carcinoids may be underreported and research on natural history is limited, but disease-related mortality is low. thNETs have a high mortality rate. Duodenopancreatic NETs (dpNETs) are multiple, almost universally found at pathology, and associated with precursor lesions. Gastrinomas are usually located in the duodenal submucosa while other dpNETs are predominantly pancreatic. dpNETs are an important determinant of MEN1-related survival, with an estimated 10-year survival of 75%. Survival differs between subtypes and apart from tumor size there are no known prognostic factors. Natural history of nonfunctioning pancreatic NETs needs to be redefined because of increased detection of small tumors. MEN1-related gastrinomas seem to behave similar to their sporadic counterparts, while insulinomas seem to be more aggressive. Investigations into the molecular functions of menin have led to new insights into MEN1-related tumorigenesis. Menin is involved in gene transcription, both as an activator and repressor. It is part of chromatin-modifying protein complexes, indicating involvement of epigenetic pathways in MEN1-related NET development. Future basic and translational research aimed at NETs in large unbiased cohorts will clarify the role of menin in NET tumorigenesis and might lead to new therapeutic options.

Context: The assessment of tumor markers for diagnosing pancreatic neuroendocrine tumors (pNET) in multiple endocrine neoplasia type 1 (MEN1) patients is advised in the current guidelines but has never been validated for this purpose., Objective: The objective of the study was to assess the diagnostic accuracy of chromogranin A (CgA), pancreatic polypeptide (PP), and glucagon for pNET in MEN1., Design: This was a diagnostic study., Setting: The study was conducted at Dutch university medical centers from 2008 to 2011, representing 90% of the total Dutch MEN1 population., Patients and Methods: Patients for whom data on tumor markers in combination with the reference standard (ie, radiological imaging) were available between 2008 and 2011 were included. The reference standard for the presence of pNET was pathology or detection on magnetic resonance imaging, computed tomography, or endoscopic ultrasound confirmed on subsequent imaging, irrespective of modality at follow-up., Main Outcome Measures: The area under the receiver-operating characteristic curve (AUC), positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, sensitivity, and specificity were calculated for each marker., Results: For the analysis of PP, CgA, and glucagon, 73, 81, and 94 patients were available, respectively. The AUC for CgA was 0.48 [95% confidence interval (CI) 0.35-0.61] with a sensitivity 0.33 and a specificity 0.73; the AUC for glucagon was 0.58 (95% CI 0.46-0.70) with a sensitivity 0.43 and a specificity 0.73; and the AUC for PP was 0.64 (95% CI 0.50-0.77) with a sensitivity 0.36 and a specificity 0.74. Age, imaging modality, tumor size, and number did not influence the outcomes., Conclusion: The diagnostic accuracy of the tumor markers CgA, PP, and glucagon for pNET in MEN1 is low.

Objective: Endocrine diseases that can be part of the rare inheritable syndrome multiple endocrine neoplasia type 1 (MEN1) commonly occur in the general population. Patients at risk for MEN1, and consequently their families, must be identified to prevent morbidity through periodic screening for the detection and treatment of manifestations in an early stage. The aim of the study was to develop a model for predicting MEN1 in individual patients with sporadically occurring endocrine tumors., Design: Cross-sectional study., Methods: In a nationwide study in The Netherlands, patients with sporadically occurring endocrine tumors in whom the referring physician suspected the MEN1 syndrome were identified between 1998 and 2011 (n=365). Logistic regression analysis with internal validation using bootstrapping and external validation with a cohort from Sweden was used., Results: A MEN1 mutation was found in 15.9% of 365 patients. Recurrent primary hyperparathyroidism (pHPT; odds ratio (OR) 162.40); nonrecurrent pHPT (OR 25.78); pancreatic neuroendocrine tumors (pNETs) and duodenal NETs (OR 17.94); pituitary tumor (OR 4.71); NET of stomach, thymus, or bronchus (OR 25.84); positive family history of NET (OR 4.53); and age (OR 0.96) predicted MEN1. The c-statistic of the prediction model was 0.86 (95% confidence interval (95% CI) 0.81-0.90) in the derivation cohort and 0.77 (95% CI 0.66-0.88) in the validation cohort., Conclusion: With the prediction model, the risk of MEN1 can be calculated in patients suspected for MEN1 with sporadically occurring endocrine tumors.

Objective: To identify the optimal surgical strategy for multiple endocrine neoplasia type 1 (MEN1)-related primary hyperparathyroidism (pHPT). To describe the course of postoperative hypoparathyroidism and to assess whether genotype is associated with persistent/recurrent pHPT., Background: Surgery is the preferred treatment in MEN1-related pHPT, but the surgical procedure of choice is still uncertain., Methods: This retrospective cohort study was performed at the Departments of Endocrinology of the University Medical Centers of Utrecht and Nijmegen, the Netherlands. Patients were selected from the Dutch MEN1 database, including all patients 16 years or older treated for MEN1 from 1990 to 2009. Data were collected by medical record review., Results: Seventy-three patients underwent parathyroid surgery. Persistent/recurrent pHPT occurred in 53% after less than 3 parathyroids resected (

Objective: Multiple endocrine neoplasia type 1 (MEN1) is a hereditary syndrome characterized by parathyroid, gastroenteropancreatic, pituitary and adrenal tumours. Cardiovascular disease has been identified as an important cause of death in MEN1 patients. Menin, the product of the MEN1 gene, is a co-activator for peroxisome proliferator-activated receptor-γ and the vitamin D receptor, which are involved in glucose metabolism. We aimed to compare insulin sensitivity and prevalence of impaired fasting glucose and diabetes mellitus between MEN1 patients and controls., Design: Cross-sectional study., Patients: Sixty-three MEN1 gene mutation carriers (44% men, mean age 41 years) from 22 kindreds and 126 unrelated controls matched for gender, age and BMI., Measurements: Fasting glucose levels were categorized and compared using WHO criteria. Homeostasis model assessment (HOMA) was used as a measure of insulin resistance., Results: Homeostasis model assessment was significantly increased in MEN1 patients compared with controls (3·0 ± 2·0 vs 2·0 ± 1·0, P < 0·05). In MEN1 patients, HOMA was associated with BMI, but not with age, calcium and gastrin levels. Using logistic regression analysis, the presence of hyperparathyroidism, pancreatic lesions and various other manifestations was not associated with HOMA. Impaired fasting glucose was more prevalent in MEN1 compared with controls (17%vs 6%, P < 0·05). Three MEN1 patients (5%) compared with four controls (3%) were diabetic (not significant)., Conclusions: Multiple endocrine neoplasia type 1 patients had decreased insulin sensitivity and higher prevalence of impaired fasting glucose compared with controls, which was unrelated to MEN1 manifestations. Impaired glucose metabolism may result in increased risk of cardiovascular disease in MEN1 patients., (© 2011 Blackwell Publishing Ltd.)

Background: The optimal surgical approach for patients with primary hyperparathyroidism (pHPT) and multiple endocrine neoplasia 1 (MEN1) is controversial. We sought to determine the optimal type of surgery for pHPT in MEN1., Methods: We collected data on clinical presentation, surgery, and follow-up for MEN1 patients with pHPT at the University Medical Center Utrecht and affiliated hospitals between 1967 and 2008. Furthermore, we performed a systematic review of the literature and meta-analysis. Surgical procedures were classified into less than subtotal (

Multiple endocrine neoplasia type 1 (MEN1) is a rare disease caused by mutations in the MEN1 gene on chromosome 11. It is characterized by the occurrence of primary hyperparathyroidism (pHPT), duodenopancreatic neuroendocrine tumours (pNET), pituitary tumours (PIT), adrenal adenomas (ADR) and neuroendocrine tumours (NET) of the stomach, bronchus and thymus. MEN1 is a syndrome with high penetrance and high morbidity. Malignant NETs are the most important cause of MEN1-related death. Since 1997 the diagnosis can be made by genetic screening. MEN1 is a complex syndrome and the endocrine manifestations cannot be viewed upon as coinciding sporadic tumours. Differences in epidemiology and pathology between MEN1-related tumours and their sporadic counterparts show that a unique approach is needed. Therefore the care for MEN1 patients should be provided by a centre of expertise. Early genetic diagnosis and periodic screening are important pillars of care. For primary hyperparathyroidism surgery is the most important treatment modality, with a subtotal parathyroid gland resection as the procedure of choice. In neuroendocrine tumours surgery also is the most important treatment modality. Selective tumour enucleation has no place in the surgical treatment of MEN1-related pNETs; the exact procedure depends on the functionality of the tumour. In MEN1-associated pituitary and adrenal adenomas, watchful waiting and medical therapy play more important roles. In the twenty-first century new developments will impact the care for MEN1 patients. These developments should be critically evaluated in clinical research with the ultimate goal of optimizing the care for MEN1 patients on an evidence base.

Objective: To determine the best surgical strategy for patients with multiple endocrine neoplasia type 2A (MEN 2A) who have primary hyperparathyroidism (PHPT)., Methods: We performed a systematic literature review and conducted a retrospective cohort study that included patients with PHPT identified from the MEN 2A database at the University Medical Center of Utrecht, Utrecht, the Netherlands, between 1979 and 2009., Results: The review describes the course of worldwide parathyroid surgical management in MEN 2A PHPT over the past 75 years, which has evolved from aggressive parathyroid resections to minimally invasive parathyroidectomy (MIP). The study cohort included 20 patients. Primary surgery for parathyroid disease in patients with MEN 2A (n = 16) included MIP (n = 6), conventional neck exploration with resection of enlarged parathyroid gland(s) (n = 4), and resection of 1 or more enlarged gland(s) during total thyroidectomy (n = 6). Thirteen patients were initially cured after the primary operation. Five patients experienced persistent or recurrent PHPT. After MIP, 1 patient had persistent PHPT, but no patient developed recurrent PHPT during 5 years of follow-up. Five patients had hypoparathyroidism after subtotal or total parathyroidectomy with autotransplantation, but only 1 patient had transient hypoparathyroidism after MIP. One patient had transient recurrent laryngeal nerve injury after MIP., Conclusions: Surgery for PHPT in patients with MEN 2A has evolved from aggressive conventional exploration of all 4 glands to focused MIP, which appears to be a feasible approach. MIP has low rates of persistent and recurrent PHPT, and the complications are minimal.

Objective: Effect of genetic screening on outcome in multiple endocrine neoplasia type 1 (MEN1) remains unclear. Expression of MEN1 is described using currently available diagnostic techniques. Manifestations and outcome are compared in patients diagnosed because of clinical expression with those diagnosed by genetic screening., Design: Retrospective cohort study. Patients are divided into two groups: patients with a (i) clinical MEN1 diagnosis and (ii) MEN1 diagnosis by genetic screening., Patients and Measurements: Demographic and clinical data were collected on MEN1 patients treated in the UMCU up to 1 January 2008. Results of mutation analysis were obtained from the Department of Medical Genetics., Results: A total of 74 patients was included (median follow-up 5.5 year); 78% had hyperparathyroidism, 46% a pancreatic neuro-endocrine tumour (NET), 38% a pituitary abnormality, 8% a NET of other origin and 16% an adrenal adenoma at the end of follow-up. Of the patients 18% had no manifestation. All five MEN1-related tumours were seen as first manifestation. Compared with patients identified by genetic screening, patients with a clinical MEN1 diagnosis had significantly more manifestations at diagnosis (P < 0.001) and at end of follow-up (P = 0.002). Eleven of 30 patients with a genetic MEN1 diagnosis (mean age at diagnosis 30.0 years) already had manifestations at diagnosis. No malignancy or death was seen in genetically diagnosed patients., Conclusions: MEN1 is a syndrome with high morbidity. Genetic diagnosis is associated with less morbidity at diagnosis and at follow-up. Early genetic diagnosis might therefore lead to improvement of long-term outcome.