Acrodysostosis is a rare genetic disorder characterized by skeletal malformations, growth delays, short stature, and distinctive facial features caused, in part, by underdeveloped (hypoplastic) of certain facial bones, particularly those in the middle portion of the face. A characteristic symptom is abnormally small hands and feet with short, stubby fingers and toes that may affect all or some of the fingers and toes. Some affected children have varying degrees of intellectual disability; in other children intelligence is unaffected. Some children experience resistance to certain hormones, which means that the tissues of the body do not respond to the hormone in question despite normal or high activity levels of the hormone. Acrodysostosis may be caused by mutations in the PRKAR1A gene (type 1) or the PDE4D gene (type 2). These mutations usually occur sporadically without a positive family history; mutations in PDE4D can be inherited in an autosomal dominant manner. It is likely that additional forms of acrodysostosis exist; caused by as-yet-unidentified gene mutations.