Allan-Herndon-Dudley syndrome

Allan-Herndon-Dudley syndrome causes moderate to severe intellectual disability and problems with movement. People with this syndrome also have impaired speech and a limited ability to communicate. Most children have weak muscle tone (hypotonia) and underdevelopment of many muscles (muscle hypoplasia). As they get older, they often develop joint deformities called contractures, which restrict the movement of certain joints. Abnormal muscle stiffness (spasticity), muscle weakness, and involuntary movements of the arms and legs also limit mobility. As a result, many people with Allan-Herndon-Dudley syndrome are unable to walk independently and use a wheelchair in adulthood.