Megalencephalic Leukodystrophy with subcortical cysts (MLC)
https://www.cureus.com/articles/494833#!/#
This case report describes a rare brain disorder called Megalencephalic Leukoencephalopathy with Subcortical Cysts (MLC), also known as Van der Knaap disease. It usually begins in infancy with an enlarged head and slow motor development. However, this case highlights an unusual presentation in a 12‑year‑old boy who developed seizures much later than expected. Despite striking abnormalities on MRI, he was still able to walk independently, showing a mismatch between severe imaging findings and relatively mild symptoms. MRI scans revealed classic features of MLC: widespread white matter swelling and cysts in the temporal and occipito‑parietal regions of the brain, including one unusually large 8‑cm cyst. Importantly, key brain structures such as the corpus callosum and internal capsule were preserved, helping distinguish MLC from similar disorders. Diffusion imaging showed vasogenic oedema, meaning fluid buildup rather than cell death. Genetic testing confirmed a pathogenic MLC1 mutation (c.135dup), a known founder mutation in certain Indian communities. A founder mutation is a mutation with high frequency in a group that is or was geographically or culturally isolated. The report emphasises the importance of combining MRI and genetic testing for accurate diagnosis, early family screening, and informed genetic counselling to reduce recurrence in future generations.