1q21.1 Microdeletion Syndrome

1q21.1 microdeletion syndrome is a chromosome abnormality where a segment of genetic material on the long arm (or q arm) of chromosome 1 at position 21.1 is missing (or deleted). Some people with this deletion have no observable features while others have variable findings that can include a small head (microcephaly), developmental delay (speech and motor delays), mild intellectual disability, distinctive facial features, and eye abnormalities. Other findings can include seizures as well as abnormalities of the heart, skeleton, and urinary system. Psychiatric and behavioral features can include autism spectrum disorders, anxiety and mood disorders, schizophrenia, attention deficit hyperactivity disorder and sleep disorders. This syndrome is caused by a deletion in a specific region of 1q21.1, which is distinct from the deletion region that causes TAR syndrome.