Several other EB registries have been established within the past few decades; summary estimates are provided in Tables 22.1 and 22.2. The first registry that may have been attempted was in South Africa in the mid-1980s, although data were never published on this cohort. More recently several other EB registries have been established in other countries, to include Italy, Germany, the Netherlands, Scotland, and Australia. The design of each of these varies somewhat, undoubtedly reflecting differences in the level of funding, accessibility of patients to more centralized evaluation, extent of clinical data being collected, and types of diagnostic testing being performed. Some are based within research units that are focused on also collecting samples for cell biological and molecular studies, thereby providing additional information that was not available to the NEBR. Others have created Web-based databases listing published and unpublished mutations for specific EB-associated genes, although these tend not to be linked to rigorously validated clinical data. Probably the largest on keratin mutations in EBS is maintained by investigators in Scotland and Singapore, whereas another database, focused on COL7A1 mutations, has been established by a group of Polish investigators [8]. A potentially inherent problem with some of these cohorts, however, is the lack of rigorous wide-scale, population-based case finding, as well as the potential for focusing primarily on the most severe forms of EB which would naturally preferentially come to their attention for diagnostic testing and medical care. Another risk in some is the use of data collected by a relatively large number of clinicians who are scattered across great geographical areas. Based on the NEBR experience with only four formal clinical centers, such a design, albeit necessary in order to obtain larger numbers of patients, runs the major risk of misclassification bias, at least at the level of clinical findings.