ACP5 and hyperostosis: These findings are consistent with previous studies showing elevated serum APase and TRAP levels in CMD patients and a CMD mouse model, suggesting increased bone formation and bone resorption resulting in increased bone turnover in CMD patients.(13,16,31) The increased bone turnover in long bones explains the osteopenic phenotype in CMD patients and the CMD mouse model, whereas the hyperostosis of the cranium results from the low bone turnover and increased bone formation.