This study seeks to delineate the clinical and molecular features of Proteus syndrome. Proteus syndrome is a sporadic disorder that includes soft and bony tissue overgrowth, mental retardation, and tumor predisposition. It is extremely rare and difficult to diagnose. We will gather affected subjects and evaluate in detail from a clinical perspective to understand the range of manifestations of the disorder and the natural history. In addition, we will use new molecular tools of subtractive cloning techniques, cDNA arrays, differential display, etc. to begin to understand the gene pathway that is perturbed in this disorder. - Mental retardation, Pediatric research, cancer research, dental/oral disease, brain disorders, clinical research, diagnostic radiology - Human Subjects