A rare, complex type of hereditary spastic paraplegia characterized by early-onset progressive spastic paraplegia presenting in infancy, associated with optic atrophy, fixation nystagmus, polyneuropathy occurring in late childhood/early adolescence leading to severe motor disability and progressive joint contractures and scoliosis. SPOAN syndrome is caused by mutations in the KLC2 gene (11q13.1), encoding kinesin light chain 2.