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. The disease is spastic paraplegia, optic atropy, and neuropathy (MONDO_0012297, a Monarch Disease Ontology identifier). Also known as: SPOAN, SPOAN syndrome, spastic paraplegia, optic atropy, and neuropathy syndrome, spastic paraplegia-optic atrophy-neuropathy syndrome.