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Megalencephalic Leukoencephalopathy with Subcortical Cysts (MLC)

What is MLC?

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is characterized by an enlarged brain that affects the development and function of the brain, along with leukoencephalopathy. Cysts often form in the cerebral cortex and can grow and multiply. 

There are three forms of MLC: Type 1, Type 2A, and Type 2B. 

This is a very rare condition, with about 150 cases being reported in medical literature. 

What are the symptoms of MLC?

This condition is progressive, meaning that symptoms worsen over time. A major symptom is muscle issues and movement problems, specifically muscle stiffness and ataxia. Other symptoms include uncontrollable muscle tensing, difficulty swallowing, involuntary limb movement, and issues with speech. More than 50% of affected individuals experience seizures. While intellectual disability is present, it is typically mild to moderate. 

It is important that head trauma is avoided, because even mild trauma can cause comas. 

What causes MLC?

A mutated MLC1 gene is responsible for Type 1 MLC, which comprises about 75% of cases. This gene is responsible for the MLC1 protein, which plays a role in glial cells, but its exact role is unknown. It is inherited in an autosomal recessive pattern. 

20% of cases are caused by a mutation in the HEPACAM gene, which results in Types 2A and 2B. This gene makes a protein called GlialCAM. Type 2A is inherited in an autosomal recessive pattern, while 2B is passed down in an autosomal dominant pattern. 

The remaining 5% of affected individuals do not have a mutation in either of these genes, and doctors are unaware of the cause. 

How is MLC diagnosed?

Doctors will notice the characteristic signs of this condition and use an MRI in order to see any abnormalities in the brain. To confirm a diagnosis, they will use genetic testing. 

What are the treatments for MLC?

There is no cure for MLC. Treatment is symptomatic and supportive. 

Where can I find out more about MLC?

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