Neurodegenerative and leukodystrophy disorders — branching viva

Opening branch — the boy with the parieto-occipital lesion

A previously well seven-year-old presents with two months of school decline, difficulty following the ball at sport, and intermittent vomiting, with an unenhanced brain MRI showing symmetric parieto-occipital white-matter change. The candidate must first recognise this as a likely cerebral X-linked adrenoleukodystrophy and name the mechanism-based classification - lysosomal and dysmyelinating, peroxisomal and inflammatory, hypomyelinating, astrocytopathic and interferonopathic - placing this disorder in the peroxisomal and inflammatory group driven by very-long-chain fatty acid accumulation and CD8 T-cell-mediated inflammation. ^{[1] [2]}

The examiner probes the management decision. The candidate states that the single addition that settles the transplant question is gadolinium contrast, because the enhancing leading edge of the inflammatory phase confirms active cerebral disease and is missed on the unenhanced scan, and that the Loes score alongside the neurological examination stages the disease. The teaching point is that allogeneic haematopoietic stem cell transplant halts the inflammation only when the burden is still low and the examination preserved, so the case is a transplant-pace emergency referred the same day. ^[2]