Whether the various Tafazzin allele differences in neutrophil phenotypes are reflective of inherent BTHS variability, a subset of BTHS patients, or are due to lower wildtype Tafazzin levels, a complete absence of Tafazzin and/or the presence of a stable TazD75H mutant protein remains to be determined. The gene discussed is TAFAZZIN; the disease is Barth syndrome.