SCA3 – Machado-Joseph Disease — SCE Neurology MCQ

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ModerateNeurogeneticsSCA3 – Machado-Joseph DiseaseSCE Neurology

A 45-year-old man of Portuguese descent presents with progressive cerebellar ataxia, ophthalmoplegia, peripheral neuropathy, and pyramidal signs. His father and paternal grandmother had similar symptoms. Genetic testing shows a CAG repeat expansion in the ATXN3 gene. What is the diagnosis?

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Correct answer: C — Spinocerebellar ataxia type 3 (Machado-Joseph disease)

SCA3 (Machado-Joseph disease) is the most common autosomal dominant spinocerebellar ataxia worldwide. It is caused by a CAG repeat expansion in the ATXN3 gene. Features include progressive cerebellar ataxia, ophthalmoplegia (including lid retraction — 'staring eyes'), pyramidal signs, peripheral neuropathy, dystonia, and parkinsonism. It is particularly common in families of Portuguese/Azorean descent. Like other polyglutamine disorders, it shows anticipation. A: FA is autosomal recessive with cardiac involvement. C: HD has chorea and psychiatric features with HTT mutations. D: EA2 is episodic with CACNA1A mutations. E: DRPLA has a different gene (ATN1).

Reference: EAN SCA Guidelines; ABN Ataxia Guidelines