SPAX4 is a neurodegenerative disorder characterized by cerebellar ataxia and spastic paraparesis. Other defining features of this condition include dysarthria and ocular anomalies such as optic atrophy and nystagmus. Patients also exhibit delayed walking, hyperreflexia of the lower limbs, brisk jaw jerk, extensor plantar responses, poor oromandibular coordination, learning difficulties, and in some cases, emotional lability. The disorder results in certain laboratory abnormalities such as defects in oxidative phosphorylation in fibroblasts and decreased amount and activity of mitochondrial complexes I and IV.
SPAX4 has an onset in early childhood. The disorder is slowly progressive and most affected patients are able to maintain independent ambulation. Treatment is mainly symptomatic and supportive. Patients may benefit from physical therapy, speech therapy and educational aids.