A rare, complex subtype of hereditary spastic paraplegia that presents in infancy with delayed motor development (i.e. crawling, walking) and is characterized by lower limb spasticity, increased deep tendon reflexes, extensor plantar responses, impaired vibratory sensation at ankles, amyotrophy and borderline intellectual disability. Additional signs may include gait disturbances, Achilles tendon contractures, scoliosis and cerebellar abnormalities.