Barth syndrome (BTHS; OMIM #302060) is a rare, infantile-onset, X-linked mitochondriopathy that exhibits a variable presentation of failure to thrive, short stature, skeletal myopathy, neutropenia, and heart anomalies due to mitochondrial dysfunction secondary to inherited TAFAZZIN (TAZ; OMIM #300394) mutations [5,6,7]. Here, TAFAZZIN is linked to Decreased total neutrophil count.