The Clinical Spectrum of Ataxia with Oculomotor Apraxia Type 2

Clinical and Genetic Characterization of Brazilian Patients with Ataxia and Oculomotor Apraxia

BACKGROUND

Ataxia with oculomotor apraxia (AOA) is characterized by early-onset cerebellar ataxia associated with oculomotor apraxia. AOA1, AOA2, AOA3, and AOA4 subtypes may present pathogenic variants in APTX, SETX, PIK3R5, and PNKP genes, respectively. Mutations in XRCC1 have been found to cause autosomal recessive spinocerebellar ataxia-26 (SCAR26) now considered AOA5.

OBJECTIVES

To examine a cohort of Brazilians with autosomal recessive cerebellar ataxia plus oculomotor apraxia and determine the frequencies of AOA subtypes through genetic investigation.

METHODS

We evaluated clinical, biomarkers, electrophysiological, and radiological findings of 52 patients with AOA phenotype and performed a genetic panel including APTX, SETX, PIK3R5, PNKP, and XRCC1.

RESULTS

We found pathogenic variants in SETX (15 patients), PNKP (12), and APTX (5). No mutations in PIK3R5 or XRCC1 were identified.

CONCLUSIONS

AOA2 and AOA4 were the most common forms of AOA in Brazil. Mutations in PIK3R5 and XRCC1 were not part of this genetic spectrum. © 2022 International Parkinson and Movement Disorder Society.

Autosomal recessive adult onset ataxia

Autosomal recessive ataxias (ARCA) represent a complex group of diseases ranging from primary ataxias to rare and complex metabolic disorders in which ataxia is a part of the clinical picture. Small number of ARCA manifest exclusively in adulthood, while majority of typical childhood onset ARCA may also start later with atypical clinical presentation. We have systematically searched the literature for ARCA with adult onset, both in the group of primary ataxias including those that are less frequently described in isolated or in a small number of families, and also in the group of complex and metabolic diseases in which ataxia is only part of the clinical picture. We propose an algorithm that could be used when encountering a patient with adult onset sporadic or recessive ataxia in whom the acquired causes are excluded. ARCA are frequently neglected in the differential diagnosis of adult-onset ataxias. Rising awareness of their clinical significance is important, not only because some of these disorders may be potentially treatable, but also for prognostic implications and inclusion of patients to future clinical trials with disease modifying agents.