Cerebellar vermis hypoplasia/aplasia, oligophrenia, ataxia, coloboma, and hepatic fibrosis, also known as COACH syndrome, is a rare genetic condition that affects many parts of the body, including the brain, eyes, and liver. COACH syndrome is the result of an abnormality in the cerebellar vermis, a part of the brain that controls coordination and balance. COACH syndrome is one of a number of disorders known as Joubert syndrome and related disorders (JSRD). Joubert syndrome is a rare genetic condition that also affects the cerebellar vermis, which is located between the left and right sides of the brain. In Joubert syndrome, the cerebellar vermis is absent or underdeveloped. These disorders share some signs and symptoms but are considered distinct syndromes.
Patients diagnosed with COACH syndrome characteristically exhibit the following features: underdevelopment (hypoplasia) or complete lack (aplasia or agenesis) of the cerebellar vermis, usually indicated by the "molar tooth" sign seen on an axial view of a magnetic resonance imaging (MRI) brain scan; developmental delays and intellectual disabilities; difficulty coordinating voluntary muscle movements; uncoordinated movements (ataxia); a malformation of the retina or other parts of the eye (coloboma); abnormalities of the liver, including hepatic fibrosis; and decreased muscle tone (hypotonia).
Although COACH syndrome is believed to be caused by a genetic mutation or defect, the exact mutation is currently not known. COACH syndrome is inherited or passed down among family members as an autosomal recessive trait. This means that an individual must inherit two copies of the defective gene for the condition to occur. No genes have been identified that specifically cause COACH syndrome. It is likely that alterations in multiple genes cause this condition.
The prevalence of COACH syndrome is not known but seems to be higher among people whose parents are closely related (consanguineous). Only about 20 cases have been reported in the scientific literature.
There is no cure for COACH syndrome. Treatment aims to reduce symptoms and prevent complications. Life expectancy of individuals with COACH depends on the severity of liver and kidney failure.
Autosomal recessive inheritance, consanguineous, Joubert syndrome, Joubert syndrome and related disorders (JSRD).