In support of the second ever Aicardi Syndrome Awareness Day, Porterhouse Medical is proud to share some vital information about the disease.
Aicardi syndrome, which primarily affects females, is an extremely rare condition with an incidence of approximately 1 in 100,000 people . Although the condition affects very few individuals, it is a devastating diagnosis; there is no cure, no standard course of treatment and a huge hole in the basic understanding of the disease .
Disease characteristics and prognosis
First identified in 1965 by French paediatric neurologist and epileptologist Dr Jean Aicardi , Aicardi syndrome is a severe neurodevelopmental disorder characterised by a triad of clinical features: agenesis of the corpus callosum, infantile epileptic seizures and chorioretinal lacunae .
Agenesis of the corpus callosum is a birth defect in which there is partial or total absence of the corpus callosum (the part of the brain that connects the left and right hemispheres). The first symptom of corpus callosum agenesis is often epileptic seizures, which is another feature in the Aicardi syndrome triad .
Infants with Aicardi syndrome typically have seizures called infantile spasms, which are single jerks of the whole body that can happen many times a day . As they get older, children usually stop having infantile spasms and instead have more common types of seizures, such as generalised tonic-clonic seizures (or ‘grand mal’) in which individuals are usually unconscious and exhibit rhythmic limb jerking .
Chorioretinal lacunae are the most consistent feature of Aicardi syndrome. They are rounded, flat lesions of the retina that are usually clustered around the optic disc. If the small part of the retina that is responsible for sharp vision – the fovea – is spared, individuals retain good vision .
Along with these classic diagnostic features, children with Aicardi syndrome are likely to have profound developmental delay, and most will have moderate to severe intellectual disability .
Aicardi syndrome is associated with high mortality. A study of 69 patients with Aicardi syndrome reported a median survival of 18.5 (± 4) years, and the oldest reported surviving individual with the disease was only 32 years old . The most common causes of death in sufferers are respiratory failure, systemic infections and sudden unexpected death in epilepsy (SUDEP) .
The mystery of Aicardi syndrome genetics
In a time when whole genome sequencing in humans is commonplace in research, it is perhaps surprising to learn that the genetics of Aicardi syndrome are not well understood. Scientists believe that the disease is caused by novel dominant mutations in a gene located on the X chromosome, but the gene has not been identified .
These deductions were made based on the fact that Aicardi syndrome usually affects females or, very rarely, males with Klinefelter syndrome (XXY chromosomes), and that there are no cases of familial recurrence. It is thought that the causative mutation in normal XY males is embryonically lethal .
It is possible that the genetic picture of Aicardi syndrome is more complex than a typical single gene-disease relationship. Researchers are considering the possibility of low-level mosaicism (different genotypes within the same individual) and balanced rearrangements (chromosomal rearrangements that are not detectable by cytogenetics). The cause could also lie in regulatory regions of DNA (i.e. not within genes) and may not be found within the genetic code at all but instead be in epigenetic changes (heritable gene changes that do not involve alterations in DNA) .
The implications of COVID-19 on Aicardi syndrome
Given how rare the disease is within all populations, it is perhaps not surprising that there is limited information regarding the specific picture for Aicardi syndrome and COVID-19. What is known is that individuals living with Aicardi syndrome are mostly children and that children typically experience COVID-19 as a mild disease . However, patients with Aicardi syndrome may have compromised immune systems; therefore, affected individuals and families in areas with high rates of COVID-19 infections are likely to be exercising extreme caution .
What you can do
The Aicardi Syndrome Foundation is the US-based not-for-profit organisation that is behind the awareness day. Donations to support children affected by this extremely rare disease can be made directly to this organisation via their website. Those who would prefer to make a donation to a UK-based organisation can support Corpal, a not-for-profit organisation for those affected by agenesis of the corpus callosum or Aicardi syndrome. There are also several charities supporting sufferers of epilepsy, such as Epilepsy Action and the Epilepsy Society.
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- National Institute of Neurological Disorders and Stroke. Aicardi syndrome information page. Available at: https://www.ninds.nih.gov/Disorders/All-Disorders/Aicardi-Syndrome-Information-Page. Accessed November 2020.
- Aicardi J, Lefebrve J and Lerique-Koechlin A. A new syndrome: Spasm in flexion, callosal agenesis, ocular abnormalities. Electroencephalogr Clin Neurophysiol 1965; 9: 609–610.
- National Organization for Rare Disorders. Aicardi syndrome. Available at: https://rarediseases.org/rare-diseases/aicardi-syndrome. Accessed November 2020.
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- Aicardi Syndrome Foundation. Fundraisers. Available at: http://aicardisyndromefoundation.org/fundraisers-2. Accessed November 2020.
Author: Luke Smith, Associate Medical Writer, Porterhouse Medical Group