Proximal 18q deletion syndrome

Proximal 18q deletion syndrome is a chromosomal condition that occurs when a piece of the long (q) arm of chromosome 18 is missing. The term "proximal" means that the missing piece occurs near the center of the chromosome. Individuals with proximal 18q deletion syndrome have a wide variety of signs and symptoms. Because only a small number of people are known to have this type of deletion, it can be difficult to determine which features should be considered characteristic of the disorder.

Most people with proximal 18q deletion syndrome have delayed development of skills such as sitting, crawling, walking, and speaking, and intellectual disability that can range from mild to severe. In particular, vocabulary and the production of speech (expressive language skills) may be delayed. Recurrent seizures (epilepsy) and weak muscle tone (hypotonia) often occur in this disorder. Affected individuals also frequently have neurodevelopmental disorders such as hyperactivity, aggression, and autism spectrum disorder that affect communication and social interaction.