Malignant transformation in a case of megalencephalic leukoencephalopathy with subcortical cysts: An extreme rarity in a rare disorder.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive inherited disorder characterized by macrocephaly, progressive motor disability, seizures, mild cognitive decline, slow progression, and typical magnetic resonance imaging (MRI) findings. Age of onset of symptoms is described from birth to 25 years. Late onset presentation is very rare, only few cases have been reported worldwide. Most important clue for diagnosis is the characteristic MRI changes that include diffuse involvement of subcortical white matter mainly in frontoparietal region with relative sparing of central white matter along with subcortical cysts mostly in anterior temporal region. Cysts are usually benign and slowly progressive. Malignant transformation of cysts has not been reported as yet. We herein report a very unusual and probably the first case of MLC who presented to us in a unique manner with late onset and malignant transformation of cyst in left temporal region leading to rapid neurological decline. This case report highlights a possible life-threatening complication of a previously known slowly progressive disease warranting urgent neurosurgical intervention.