High quality research in rare diseases remains challenging due to the low incidence and prevalence. However, there is a need for scientific evidence to formulate evidence-based guidelines in order to provide physicians with tools for clinical practice. The rare endocrine tumor syndrome multiple endocrine neoplasia type 1 (MEN1) is a good example, being a genetic disease with an autosomal dominant inheritance and an estimated occurrence rate of 2–3 per 100.000.
MEN1 is characterized by the classical triad of primary hyperparathyroidism, duodenopancreatic neuroendocrine tumors and pituitary adenomas. Other encountered neoplasms include adrenal tumors, neuroendocrine tumors of thymic, bronchial or gastric origin, skin and subcutaneous tumors, smooth muscle tumors, and breast cancer.
Insight into predictors of the natural course and prognosis of the individual MEN1 related manifestation will lead to timely tumor detection, improved individualized patient management and targeted treatment. Since randomized controlled trials are difficult to perform due to the limited number of patients and the low incidence of events in individual patients, at this time, cohort studies are the highest level of scientific evidence. Brandi, et al. have performed a nationwide cohort study including 14 referral centers from 12 different Italian cities. The authors underline that cohort studies based on national databases and registries are of pivotal importance for clinical and translational research and knowledge in the field of rare diseases. Efforts to work on a national registry are strenuous, but also rewarding in the case of rare diseases. The authors have found similar findings in occurrence of tumors and mortality as other national cohorts. This is an important finding, which stretches out that the results from one cohort seem generalizable to other MEN1 cohorts. This is an important finding before moving towards supranational collaborations.
Other European countries with well-known national MEN1 databases are the Group d’etude des Tumeurs Endocrine in France and the Dutch MEN1 Study Group (DMSG) in The Netherlands. These cohorts have respectively 924 and 393 MEN1 patients in their national registries. The DMSG has a database which covers > 90% of the total Dutch MEN1 population, making it a true population-based registry and hereby reducing the chance of selection bias leading to new insights into the natural course of the disease.
The need for international data-registries is also expressed by the European Union Committee of Experts on Rare Diseases. The next steps would be the collaboration between the national registries which will give access to the clinical data of almost 2000 MEN1 patients. An international collaboration would expand the MEN1 population in which randomized clinical trials seem to become possible. This need is not only expressed by policymakers and physicians, but also by the national and European MEN1 patient advocacy groups who support these supranational collaboration in order to further improve the guidelines and eventually care for patients with MEN1.

Additional Metadata
Persistent URL dx.doi.org/10.1007/s12020-017-1296-3, hdl.handle.net/1765/99252
Journal Endocrine : International Journal of Basic and Clinical Endocrinology
van Leeuwaarde, R.S, de Herder, W.W, & Valk, G.D. (2017). The need for national registries for rare endocrine tumor syndromes. Endocrine : International Journal of Basic and Clinical Endocrinology, 1–2. doi:10.1007/s12020-017-1296-3