Xia-Gibbs syndrome

Xia-Gibbs syndrome is a rare neurodevelopmental disorder marked by low muscle tone, delayed development and intellectual disability that ranges from mild to severe. Speech is hit hardest: many children say no first word until age two or later, and some never talk. Other features vary from person to person and can include seizures, poor balance and coordination, feeding difficulties, sleep problems including obstructive sleep apnea, short stature, scoliosis and a thin corpus callosum on brain imaging. Some people have distinctive facial features, and some have autism spectrum disorder or attention-deficit/hyperactivity disorder. The syndrome is caused by new variants in the AHDC1 gene, usually producing shortened proteins, and follows an autosomal dominant pattern. Its true frequency is unknown, and it is probably underdiagnosed.