Spinocerebellar Ataxia (SCA)

Case Study A
A 35-year-old woman presented with progressive gait difficulties and speech difficulties since the age of 28. There was a strong family history of a similar disorder inherited in a dominant fashion. On examination, mental status and language were normal. There was mild scanning dysarthria. There was no visual loss and fundi were normal. Examination of eye movements revealed mild slowing of saccades, gaze-evolved nystagmus, and mild restriction of upgaze. There was no facial atrophy or perioral fasciculation; tongue was normal. Muscle strength, tone, and bulk were normal and there was no rigidity or tremor of any kind. Rapid alternating movements were slowed and clumsy, and there was mild finger-to-nose and considerable heel-to-shin ataxia. Deep tendon reflexes were uniformly brisk, and gait was ataxic, but the plantar responses were flexor.

MRI of the brain showed pontocerebellar atrophy. Analysis of the CAG repeats in the MJD locus revealed a normal allele with 36 repeats and an expanded allele with 78 repeats. Therefore, the diagnosis of Machado-Joseph Disease (MJD) was made.