X-linked spastic paraplegia due to a mutation (C506T; Ser169Phe) in exon 4 of the proteolipid protein gene (PLP).

A transition C506T was found in exon 4 of the proteolipid protein gene of a boy with spastic paraplegia. This mutation resulted in the substitution of phenylalanine for serine 169, which is in the third transmembrane domain of the proteolipid protein molecule. The mutation apparently arose de novo, as it was absent from his mother.