Megalencephalic Leukoencephalopathy with Subcortical Cysts, MLC1 Related

Gene : MLC1

What is Megalencephalic Leukoencephalopathy with Subcortical Cysts?

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a very rare disorder of the brain. Individuals who have MLC are typically either born with or develop a large head early in the first year of life. Early development, such as walking, is typically normal or mildly delayed; however, a slow deterioration of motor skills starts in early childhood, and most children affected with this disorder will require a wheelchair sometime during their teenage years. Intellectual disability is mild and speaking and swallowing difficulties can also develop. Most of these individuals will have epileptic seizures that can be controlled with medicine. Some individuals have died in adolescence, and some have survived into their 40s. There is no cure for MLC; however medical surveillance and care may help to improve some symptoms and overall condition of life. MLC is caused by pathogenic variants in the MLC1 gene.

How is megalencephalic leukoencephalopathy with subcortical cysts inherited?

MLC is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant in the gene for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

What does it mean to be a carrier?

There are generally no signs or symptoms associated with being a carrier for MLC. However, the risk to have a child affected with MLC is increased. Testing of reproductive partners is recommended for carriers of MLC syndrome.

How common is megalencephalic leukoencephalopathy with subcortical cysts?

The frequency of MLC, which is extremely rare, is currently unknown in the general population.

Family References and Resources
Clinician References
What is Analyzed?
  • Full gene sequencing
Affected Systems



Carrier Rates
Detection Rate
Carrier Frequency
General Population > 81% 1 in 500

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