Other disorders included benign cortical defect of tibia (28), hexadactyly with a complete second thumb (4), polyostotic fibrous dysplasia (7), bone hyperplasia (16) or hypoplasia (31), osteosclerosis (23, 24), scoliosis (14), plagiocephaly (17), and maldevelopment of bone (12) and were associated with mutations in the KRAS (8 cases) or HRAS (2 cases) genes, respectively (Figure 4D). Here, HRAS is linked to polyostotic fibrous dysplasia.