Novel variants in AP4B1 cause spastic tetraplegia, moderate psychomotor development delay and febrile seizures in a Chinese patient: a case report

INTRODUCTION: The AP4B1 gene encodes a subunit of adaptor protein complex-4 (AP4), a component of intracellular transportation of proteins which plays important roles in neurons. Bi-allelic mutations in AP4B1 cause autosomal recessive spastic paraplegia-47(SPG47). CASE PRESENTATION: Here we present a Chinese patient with spastic tetraplegia, moderate psychomotor development delay and febrile seizures plus. Brain MRIs showed dilated supratentorial ventricle, thin posterior and splenium part of corpus callosum. The patient had little progress through medical treatments and rehabilitating regimens. Whole exome sequencing identified novel compound heterozygous truncating variants c.1207C > T (p.Gln403*) and c.52_53delAC (p.Cys18Glnfs*7) in AP4B1 gene. Causal mutations in AP4B1 have been reported in 29 individuals from 22 families so far, most of which are homozygous mutations. CONCLUSIONS: Our study enriched the genetic and phenotypic spectrum of SPG47. Early discovery, diagnosis and proper treatment on the conditions generally increase chances of improvement on the quality of life for patients.