Barth syndrome (BTHS) is a rare genetic disease caused by mutations in the TAFAZZIN gene. It is characterized by neutropenia, cardiomyopathy, and skeletal myopathy. Neutropenia in BTHS is associated with life-threatening infections, yet the molecular and physiological causes of this phenomenon are poorly understood. We conducted proteome analysis of circulating neutrophils from BTHS patients to identify upregulated and downregulated canonical pathways that may explain the disruptions in neutrophil maturation and function.