GTR Home > Conditions/Phenotypes > Megalencephalic leukoencephalopathy with subcortical cysts 2b, remitting, with or without mental retardation
The classic phenotype of megalencephalic leukoencephalopathy with subcortical cysts (MLC) is characterized by early-onset macrocephaly, often in combination with mild gross motor developmental delay and seizures; gradual onset of ataxia, spasticity, and sometimes extrapyramidal findings; and usually late onset of mild mental deterioration. Macrocephaly, observed in all individuals, may be present at birth but more frequently develops during the first year of life. The degree of macrocephaly is variable and can be as great as 4 to 6 SD above the mean in some individuals. After the first year of life, head growth rate normalizes and growth follows a line parallel to the 98th percentile, usually several centimeters above it. Almost all individuals have epilepsy from an early age. Initial mental and motor development is normal in most cases. Walking is often unstable, followed by ataxia of the trunk and extremities, then minor signs of pyramidal dysfunction and brisk deep-tendon stretch reflexes. Mental deterioration is late and mild. Severity ranges from independent walking for a few years only to independent walking in the fifth decade. Some individuals have died in their teens or twenties; others are alive in their forties. An atypical improving phenotype has a similar initial presentation without mental or motor regression, followed by an improving clinical course: motor and cognitive functions improve or normalize; macrocephaly usually persists, but some children become normocephalic; hypotonia and clumsiness may persist in some or neurologic examination may become normal. Some have intellectual disability that is stable with or without autism.

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