Septo-optic dysplasia (SOD), known also as de Morsier syndrome, is a rare congenital malformation syndrome that features a combination of the underdevelopment of the optic nerve, pituitary gland dysfunction, and absence of the septum pellucidum (a midline part of the brain).
Two or more of these features need to be present for a clinical diagnosis—only 30% of patients have all three. French-Swiss doctor Georges de Morsier first recognized the relation of a rudimentary or absent septum pellucidum with hypoplasia of the optic nerves and chiasm in 1956.
Signs and symptoms
The symptoms of SOD can be divided into those related to optic nerve underdevelopment, pituitary hormone abnormalities, and mid-line brain abnormalities. Symptoms may vary greatly in their severity.
Optic nerve underdevelopment
About one quarter of people with SOD have significant visual impairment in one or both eyes, as a result of optic nerve underdevelopment. Developmental delays are more common in children with bilateral optic nerve hypoplasia than those with unilateral optic nerve hypoplasia.
There may be nystagmus (involuntary eye movements, often side-to-side).
Mid-line brain abnormalities
In SOD, mid-line brain structures such as the corpus callosum and the septum pellucidum may fail to develop normally, leading to neurological problems such as seizures or developmental delay. Five homozygous and eight heterozygous pathogenic HESX1 mutations have been discovered. Patients with homozygous mutations present with a typical SOD phenotype while those with heterozygous mutations are mildly affected.
History
In 1941 David Reeves at the Children's Hospital Los Angeles described an association between underdevelopment of the optic nerve with an absent septum pellucidum. Fifteen years later French doctor Georges de Morsier reported his theory that the two abnormalities were connected and coined the term septo-optic dysplasia. In 1970 American doctor William Hoyt made the connection between the three features of SOD and named the syndrome after de Morsier.
In popular culture
British model and television personality Katie Price's son, Harvey, has this condition.