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McDonald DIS – Optic Radiation Location — SCE Neurology MCQ

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HardMultiple Sclerosis & CNS InflammationMcDonald DIS – Optic Radiation LocationSCE Neurology

A 36-year-old develops chorea, seizures, areflexia and prominent feeding dystonia with repeated tongue biting. Creatine kinase is 1,800 U/L, blood film shows occasional acanthocytes, and Kell red-cell antigen expression is normal. Which molecular result would establish the leading diagnosis?

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Correct answer: C — Biallelic loss-of-function variants in VPS13A

Explanation lettering: E = shown as A · A = shown as B · B = shown as C · C = shown as D · D = shown as E

A causes Huntington disease but does not explain the characteristic feeding dystonia, tongue biting, hyperCKaemia and areflexia. B is correct: biallelic VPS13A loss-of-function variants establish VPS13A disease, formerly chorea-acanthocytosis; acanthocytes may be sparse or absent. C causes McLeod syndrome, in which the XK defect alters Kell-system antigen expression. D causes pantothenate-kinase-associated neurodegeneration, usually with iron accumulation on MRI. E causes PLA2G6-associated neurodegeneration, another neurodegeneration-with-brain-iron-accumulation phenotype.

Reference: VPS13A disease: https://www.ncbi.nlm.nih.gov/sites/books/NBK1387/