CC2D2A-related disorders affect a part of the cell called cilia. Cilia are tiny hair-like structures on cells that help with movement and sensing things. When the cilia don’t work properly, it causes the symptoms seen in CC2D2A-related disorders.
The main CC2D2A-related disorders are Joubert syndrome and Meckel syndrome:
Joubert Syndrome: People with Joubert syndrome usually have developmental delays, low muscle tone (hypotonia), problems with balance and coordination (ataxia), and unusual eye movements. A key feature of this syndrome is a unique brain shape called the “molar tooth sign,” which can be seen on brain imaging. Most people with Joubert syndrome reach milestones later than usual and may have intellectual disabilities that can range from mild to severe. Other possible symptoms include breathing problems (especially in newborns), kidney and liver issues, feeding difficulties, extra fingers and toes, vision loss, and behavioral disorders.
Meckel Syndrome: Meckel syndrome (also known as Meckel-Gruber syndrome) is the most severe CC2D2A-related disorder. Babies with Meckel syndrome have serious birth defects, including problems with the brain, liver, and kidneys. They often have extra fingers and toes, and other issues like heart defects, cleft lip and palate, underdeveloped lungs, and bone abnormalities.
There is no cure for CC2D2A-related disorders. Treatment focuses on managing each person’s symptoms. For Joubert syndrome, early intervention and supportive services starting at a young age can help. Some babies with Joubert syndrome may need extra oxygen or a breathing tube to help with breathing. Medications might be given to help manage breathing, liver, or kidney problems. Unfortunately, babies with Meckel syndrome are usually stillborn or die shortly after birth. Treatment in these cases is focused on making the baby as comfortable as possible.
This group of conditions is caused by pathogenic (disease-causing) variants in the CC2D2A gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance of having a child with the condition.
Resources:
Joubert Syndrome & Related Disorders Foundation
Written August 2024
