Fucosidosis
https://www.cureus.com/articles/497493#!
Fucosidosis is an extremely rare inherited disorder caused by the lack of an enzyme called α‑L‑fucosidase, which leads to the buildup of certain sugars in the brain and other organs. This case report follows an 18‑year‑old girl over 15 years, showing how her brain scans changed as the disease progressed. Early MRI scans at 23 months showed hyperintensity in the supratentorial compartment of the brain which is responsible for higher-level cognitive function and a hallmark of poor myelin development. Hyperintensity are areas that appear brighter due to changes in the structure or water content of the white matter due to the blood-brain barrier being affected. Subtle changes were also seen in a deep brain structure called the globus pallidus, which later became a key diagnostic clue. T1-weighted and T2-weighted MRI are different imaging sequences that change how the images appear, T1 highlights anatomical features and fat with liquids showing dark whereas T2 highlights inflammation or swelling with fluids looking bright. Over time, her scans revealed worsening involvement of the basal ganglia, including T1 and T2 signal changes and dark areas on susceptibility imaging, indicating abnormal mineral buildup. These changes eventually extended to the substantia nigra and red nuclei (structures in the basal ganglia which control movement), showing widespread metabolic injury. One distinctive feature, medial medullary lamina (layers of myelinated fibres on the thalamus) hyperintensity became more visible over the years and helped differentiate fucosidosis from other leukodystrophies. Genetic testing at age 14 confirmed pathogenic FUCA1 mutations. The report highlights how long‑term MRI follow‑up can reveal the evolving pattern of white matter damage and deep grey matter mineralisation, guiding earlier diagnosis, targeted testing, and appropriate family genetic counselling.