Accurate DNA-based diagnostic and carrier testing for X-linked adrenoleukodystrophy

Abstract

X-linked adrenoleukodystrophy is a serious and often fatal disorder, affecting the white matter of the nervous system, the adrenal cortex, and the testis. The gene mutated in X-ALD encodes a peroxisomal membrane protein, ALDP. The presence of very long chain fatty acids in plasma is highly diagnostic for affected males and carrier females, but exclusion of carrier status biochemically is unreliable. Molecular analysis of the X-ALD gene has the potential to either identify or rule out carrier status accurately, but is complicated by the existence of autosomal paralogs. We have developed and validated a robust DNA diagnostic test for this disorder involving nonnested genomic amplification of the X-ALD gene, followed by fluorescent dye-primer sequencing and analysis. This protocol provides a highly reliable means of determining carrier status in women at risk for transmitting X-ALD and is applicable to a clinical diagnostic laboratory.