1p36 deletion syndrome is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features.

[1] The condition is caused by a genetic deletion (loss of a segment of DNA) on the outermost band on the short arm (p) of chromosome 1.

[3][4] Most people with 1p36 deletion syndrome have some structural abnormality of the brain, and approximately half have epilepsy or other seizures.

[3] The most common visual abnormalities associated with 1p36 deletion syndrome include farsightedness (hypermetropia), myopia (nearsightedness), and strabismus (cross-eyes).

These features may include microcephaly (small head), which may be combined with brachycephaly (short head); small, deep-set eyes; straight eyebrows; epicanthal folds; a broad, flat nose and nasal bridge; underdevelopment of the midface (midface hypoplasia); a long philtrum; pointed chin; and abnormally shaped, rotated, low-set ears.

20% of patients with 1p36 deletion syndrome inherit the disease from one parent who carries a balanced or symmetrical translocation.

[4] 1p36 deletion syndrome is usually suspected based on the signs and symptoms and confirmed by fluorescence in situ hybridization (FISH).