AP4B1-associated hereditary spastic paraplegia: Expansion of clinico-genetic phenotype and geographic range

•Mutations in genes that encode subunits of the adaptor protein complex 4 (AP-4) can lead to hereditary spastic paraplegias.•Disease-causing variants in the AP4B1 gene have been expanding in a number and geographic range.•Exome sequencing was performed on 7 patients from 3 Azerbaijani and Pakistani families with hereditary spastic paraplegia.•Reported cases expand the clinico-genetic phenotype and geographic range of AP4B1-associated hereditary spastic paraplegia.