DDHD1 and hereditary spastic paraplegia: Multiple joint contractures can be seen in some forms of autosomal recessive (AR) HSP including SPG18 caused by mutations in the ERLIN2 gene, SPG28 with biallelic DDHD1 (Phoshatidic acid-preferring phospholipase A1) mutations, and SPG43 with mutations in the C19ORF12 gene among others [2,3].