Objective: We investigated if Growth and Differentiation Factor 15 (GDF-15) can be used as a biomarker to distinguish patients with mitochondrial myopathy from patients with other myopathies. Methods: Serum GDF-15 was measured in 28 patients with mitochondrial disease, 24 with metabolic myopathies, 27 with muscular dystrophy and 21 healthy controls. Results and conclusions: Our findings indicate that elevated GDF-15 can distinguish patients with mitochondrial myopathy from other myopathies, including metabolic myopathies. This suggests that increases in GDF-15 is specific to respiratory chain dysfunction rather than general metabolic dysfunction or muscle defect.