We aim to delineate the range of severity, natural history, molecular etiology, and pathophysiology of Pallister-Hall syndrome (PHS), Greig cephalopolysyndactyly syndrome (GCPS), McKusick-Kaufman syndrome (MKS), Bardet-Biedl syndrome (BBS), Oro-facial digital syndromes (OFDs), and other overlapping phenotypes. These disorders comprise a syndrome community of overlapping manifestations and we hypothesize that this is a reflection of a common mechanistic pathway. This hypothesis be addressed by a combined clinical-molecular approach where we bring up to 50-100 patients with each disorder to the NIH clinical center for a comprehensive clinical evaluation with follow-up at a frequency appropriate to the disorder. Specimens will be collected and evaluated in the laboratory by linkage analysis, physical mapping, candidate gene characterization, mutation screening, and cell biologic studies of normal mutant proteins.