Allan-Herndon-Dudley syndrome

Allan-Herndon-Dudley syndrome is a rare disorder of brain development that causes moderate to severe intellectual disability and problems with movement. This condition, which occurs exclusively in males, disrupts development from before birth. Although affected males have impaired speech and a limited ability to communicate, they seem to enjoy interaction with other people.

Most children with Allan-Herndon-Dudley syndrome have weak muscle tone (hypotonia) and underdevelopment of many muscles (muscle hypoplasia). As they get older, they usually 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 become wheelchair-bound by adulthood.

Other names

Allan-Herndon syndrome; MCT8 (SLC16A2)-specific thyroid hormone cell transporter deficiency; Mental retardation, X-linked, with hypotonia; Monocarboxylate transporter 8 (MCT8) deficiency

Inheritance pattern

X-linked recessive

Related genes

SLC16A2

Source: MedlinePlus Genetics, U.S. National Library of Medicine.