Genetic features:
(1) The phenotypic frequency is around 1 in 30,000 to 50,000, while the frequency of occult microdeletions is higher.
(2) It may occur as a de novo mutation or be inherited from a parent with a cryptic translocation.
(3) The critical region for the phenotype is within band 4p16.3
Facial phenotypic features ("Greek helmet", aka hoplite):
(1) frontal bossing
(2) high frontal hair line
(3) prominent glabella (in midsagittal plane between the eyebrows)
(4) ocular hypertelorism
(5) proptosis associated with hypoplasia of the orbital ridges
(6) slanted palpebral fissures
(7) epicanthal folds
(8) strabismus
(9) broad and beaked nose
(10) prominent nasal bridge
(11) shallow nasal septum
(12) large, low set ears, often with preauricular tags or pits
(13) downturned mouth with short upper lip and philtrum
(14) micrognathia
(15) cleft lip and/or cleft palate
(16) coloboma of the iris
Other findings:
(1) cardiac septal defects
(2) urogenital malformations in males (hypospadias, scrotal hypoplasia, cryptorchidism, testicular hypoplasia)
(3) increased susceptibility to infections
(4) prenatal growth retardation
(5) severe mental retardation if survives infancy
