The American Journal of Medical Genetics Part C, is pleased to produce and publish this issue of Seminars in Medical Genetics, Very rare defects, What can we learn? The Guest Editors, Drs. Castilla and Mastroiacovo, and their colleagues have compiled an interesting series of articles on eight uncommonly occurring congenital malformations, all of which are certainly defects of blastogenesis [Opitz et al., 2002] and most of which have a birth prevalence of less than in 100,000 births.
This issue of the Seminars is a unique contribution to AJMG Part C for two reasons: First, the impressive number of authors on all of the papers covering the very rare defects. The reason for the multi-authored articles is related to the other distinctive component of these papers, i.e., the collaborative research (see below). Because of the large number of authors, we broke from the usual tradition of the Seminars and included the traditional biographical piece only for the first author of each paper.
The second reason why this is a novel issue of AJMG Seminars is the inclusion of original epidemiologic data from the International Clearinghouse for Birth Defect Surveillance and Research (ICBDSR). While there are numerous exceptions to this point about original research in Seminas articles, AJMG Part C papers ordinarily consist of review articles focusing on the issue's chosen theme. Drs. Castilla and Mastroiacovo have indeed collected a series of review articles: all of the papers follow a particular format that features a literature summary of the embryology and epidemiology of each rare defect. The novel aspect of this series is the inclusion of previously unpublished data on the epidemiology of each defect derived from ICBDSR data sets. The Editors summarize the objectives of this issue and the similar methodologies used by all the authors in their Introduction, which is a contribution to our knowledge of rare defects in and of itself. All of the works in the issue represent a collaborative effort orchestrated by the Guest Editors. Given the notable rarity of these individual malformations, the authors could not have adequately addressed the question, “What can we learn?” without combining the reviews with multicenter ICBDSR data.
We applaud the Editors and their colleagues for embracing the challenge of providing potentially new insights into the cause and pathogenesis of these particularly rare anomalies.