Megalencephalic leukoencephalopathy with subcortical cysts

Megalencephalic leukoencephalopathy with subcortical cysts (MLC, or Van der Knaap disease) is a form of hereditary CNS demyelinating disease. It belongs to a group of disorders called leukodystrophies. It is characterized by early-onset enlargement of the head (macrocephaly) as well as delayed-onset neurological deterioration to include spasticity, epilepsy, and lack of muscular coordination.^[1] MLC does not appear to be a disease that is fatal at birth or early in life despite its symptoms, although the number of patients throughout history known to have the disease is fairly limited.^[1]

It belongs to a group of disorders called leukodystrophies. A series of cases with megalencephalic leukodystrophy were described by the Indian neurologist Bhim Sen Singhal (1933-) in 1991. However, it is sometimes referred to as Van der Knaap disease after the Dutch neurologist Marjo van der Knaap who described another series of cases with clinical and radiological features in 1995.^[2]

There are three types of Megalencephalic leukoencephalopathy distinguished by the affected gene: Type 1 caused by autosomal recessive mutations on the MLC1 gene, Type 2A an autosomal recessive mutation on the HEPACAM gene, and Type 2B an autosomal dominant mutation on the HEPACAM gene.^[1]