Targeted gene approach with biochemical assay confirms ABCD1 mutation of X-linked adrenoleukodystrophy in a 62-year-old man with gait imbalance

X-linked adrenoleukodystrophy caused by a novel mutation presenting with various phenotypes in a Taiwanese family

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder that primarily affects the white matter of central nervous system and the adrenal cortex. It is caused by mutations in the adenosine triphosphate-binding cassette, subfamily D, member 1 (ABCD1) gene that results in elevated plasma levels of very long chain fatty acids (VLCFAs). The disease is characterized by an unpredictable variation in phenotypic expressions, including childhood cerebral form (CCALD) and adrenomyeloneuropathy (AMN). Genetic analysis is a reliable method for the diagnosis of X-ALD. We reported a 46-year-old male admitted to Department of Neurology, Chang Gung Memorial Hospital with progressive paraparesis and Addison's disease, which was diagnosed when he was around 20-year-old. Plasma levels of VLCFA showed that his C26:0, C24:0/C22:0 and C26:0/C22:0 ratios were significantly elevated. A novel missense mutation (p.Arg163Cys) caused by the nucleotide change c.487C > T in exon 1 was identified in the ABCD1 gene of the proband and his subclinical family members. In this article, we reviewed the mutations that had been reported at the same position with different phenotypes. Given that the nerve conduction study (NCS) of the proband demonstrated a rare finding of demyelinating polyneuropathy with conduction blocks, we also reviewed the findings of NCS in patients with AMN in literature.