Exome sequencing released a case of X-linked adrenoleukodystrophy mimicking recessive hereditary spastic paraplegia

Genetic heterogeneity is common in many Mendelian disorders such as hereditary spastic paraplegia (HSP), which makes the genetic diagnosis more complicated. The goal of this study was to investigate a Chinese family with recessive hereditary spastic paraplegia, of which causative mutations could not be identified using the conventional PCR-based direct sequencing. Next-generation sequencing of all the transcripts of whole genome exome, after on-array hybrid capture, was performed on two affected male subjects (the proband and his brother). A missense mutation (c.1661G>A, p.R554H) was identified in ABCD1. Subsequently, PCR-based direct sequencing of other family members revealed that the mutation was co-segregating with the disease, indicating that ABCD1 mutation was the pathogenic event for this family. Very long-chain fatty acids (VLCFA) assay in the two affected cases confirmed X-ALD. Our study suggests exome sequencing can be used not only to find a novel causative gene, but also to quickly identify mutations of known genes when the clinical elements are etiologically misleading.