Rare Genetic Diseases: Aicardi Syndrome

Aicardi syndrome occurs almost exclusively in females. Around 4,000 cases of individuals infected with this disease have been recorded worldwide. Although the exact gene causing this disease is unknown, research still managed to discover a lot about it.

Aicardi syndrome causes the absence or underdevelopment of the tissue connecting the left and the right side of the brain (anagenesis or dysgenesis of the corpus callosum). Furthermore, affected individuals suffer from seizures which begin during infancy (infantile spasm), as well as defects in the light-sensitive tissue at the back of the eye (chorioretinal lacunae).

Further symptoms include the asymmetry between the sides of the brain, cysts, enlargement of the fluid-filled cavities (ventricles) near the center of the brain. Moreover, patients have small or poorly developed eyes (microphthalmia), gap or hole in the optic nerve (coloboma) which functions as the transmitter of the information carried from the eye to the brain. Facial features of Aicardi syndrome consist of large ears, and a short area between the upper lip and the nose (philtrum).

The mutated gene is believed to be located on the X chromosome. The mutation occurs in a sporadic manner, which means that it mostly occurs in individuals with no history of this disease. The mutation is X-linked dominant. It can only occur in females as they have two copies of the X chromosome, unlike males, who only have one X chromosome. However, there are few records of male patients affected by Aicardi syndrome, due to their second X chromosome. These males then have X,X,Y chromosomes.

There is no treatment for this disorder. Individuals, with milder symptoms, live past childhood. However, children with severe symptoms develop epilepsy and die as a result of the frequent seizures.