Inheritance: autosomal recessive or sporadic
Gene affected: aprataxin (APTX)
Chromosome location: 9p13.3
Clinical features:
(1) onset during childhood or adolescence
(2) slowly progressive cerebellar ataxia, which usually presents with gait ataxia
(3) oculomotor apraxia that progresses to an external ophthalmoplegia
(4) axonal motor polyneuropathy with muscle atrophy in the hands and feet
(5) dysarthria
(6) upper limb dysmetria with mild intention tremor
(7) areflexia
(8) eventual development of quadriplegia with loss of ambulation
(9) chorea and upper limb dystonia are common
Laboratory findings:
(1) hypoalbuminemia is seen in most patients 10 or more years after onset
(2) serum alpha-fetoprotein normal
Imaging findings:
(1) Cerebellar atrophy may be present at symptom onset or develop over time.
Differential diagnosis:
(1) other hereditary ataxia (Friedreich's ataxia, etc)
(2) hereditary ataxia-telangiectasia
The diagnosis is excluded with:
(1) nonprogressive ataxia
(2) microcephaly
(3) seizures
