Barth syndrome, a disorder of dilated cardiomyopathy and neutropenia, is caused by mutations in TAZ on chromosome Xq28. Analysis of the genomic sequence of this gene has revealed that about 45% of the sequence is composed of SINES and LINES and three quarters of these interspersed repeat sequences are Alu sequences. Ferri et al. (Orphanet J Rare Dis, 2013, 8(1): 27) postulates that due to the high content Alu repeat sequences, TAZ rearrangements, which may appear to be similar in different patients based on the specific deleted exons, may actually be private mutations. Knowledge of the composition of the genomic sequence and susceptibilities to rearrangements is particularly important in confirming clinical diagnosis based on molecular testing, where exon deletions may be difficult to confirm.

Hilary Vernon, MD PhD