A rare, complex type of hereditary spastic paraplegia characterized by progressive spastic paraplegia (presenting in early childhood) associated with delayed motor development, severe intellectual disability and joint contractures. A thin corpus callosum is equally noted on brain magnetic resonance imaging. SPG18 is caused by a mutation in the ERLIN2 gene (8p11.2) encoding the protein, Erlin-2. The disease is hereditary spastic paraplegia 18 (MONDO_0012639, a Monarch Disease Ontology identifier). Also known as: ERLIN2 autosomal recessive complex spastic paraplegia, SPG18, autosomal recessive complex spastic paraplegia caused by mutation in ERLIN2, autosomal recessive spastic paraplegia 18, autosomal recessive spastic paraplegia type 18, hereditary spastic paraplegia type 18, intellectual disability, motor dysfunction and joint contractures.