Megalencephalic Leukoencephalopathy with Subcortical Cysts (MLC) is a disease causing seizures and developmental delay in infants, later leading to a decline in motor skills and intellectual abilities.
Changes in brain structure, like cysts visible on scans, are common. Babies with MLC often have large heads, which may normalize after the first year. They may walk independently for some years, but motor skills decline over time, and many eventually need wheelchairs. Intellectual decline comes later. While there’s no cure, treatments focus on symptom management with medications for seizures and physical therapy for motor skills.
MLC is caused by pathogenic (disease-causing) variants in the MLC1 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Sephardic Jewish descent have a 1 in 40 chance to be a carrier.
Other names for this condition are infantile leukoencephalopathy and megalencephaly, leukoencephalopathy with swelling and cysts, vacuolating megalencephalic leukoencephalopathy with subcortical cysts, and Van der Knaap disease.
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Revised November 2023
