Ataxia with Oculomotor Apraxia Type 2

Excerpt

Clinical characteristics: Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by onset of ataxia between age three and 30 years after initial normal development, axonal sensorimotor neuropathy, oculomotor apraxia, cerebellar atrophy, and elevated serum concentration of alpha-fetoprotein (AFP).

Diagnosis/testing: The diagnosis of AOA2 is based on clinical, laboratory, and radiographic features; family history; and exclusion of the diagnosis of ataxia-telangiectasia, AOA1, and AOA4. Identification of biallelic pathogenic variants in SETX by molecular genetic testing confirms the diagnosis.

Management: Treatment of manifestations: Physical therapy for disabilities resulting from peripheral neuropathy; wheelchair for mobility as needed; educational support (e.g., computer with speech recognition and special keyboard for typing) to compensate for difficulties in reading (caused by oculomotor apraxia) and in writing (caused by upper-limb ataxia).

Preventions of secondary complications: A low-cholesterol diet is advised.

Surveillance: Routine follow up with a neurologist.

Genetic counseling: AOA2 is inherited in an autosomal recessive manner. Each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk family members and prenatal diagnosis for pregnancies at increased risk are possible if the pathogenic variants in the family have been identified.