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.
Keywords: ABCD1 gene; Genetic heterogeneity; Hereditary spastic paraplegia; Whole-exome sequencing.
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