PDE4D and acrodysostosis: The other gene is PDE4D which is already reported to encode a cyclic AMP (cAMP) regulator which places PDE4D-related acrodysostosis in the same family of diseases as pseudohypoparathyroidism, pseudohypoparathyroidism, PRKAR1A-related acrodysostosis, and brachydactyly mental retardation syndrome, which are all characterized by cognitive impairment and short distal extremities (Lynch et al., 2013).