Tafazzin gene (TAZ) was originally identified as one of the genes responsible for Barth syndrome (BTHS, MIM# 302060), a severe X-linked disease characterized by mitochondrial cardiomyopathy, neutropenia, skeletal muscle weakness and growth retardation (Barth et al., 1983, Bione et al., 1996). Here, TAFAZZIN is linked to neutropenia.