In a cohort of 48 patients diagnosed with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), Leigh syndrome or Kearns-Sayre syndrome (KSS), serum GDF-15 had an impressive diagnostic sensitivity and specificity nearing 100% and AUC of 0.997 [69]. The gene discussed is GDF15; the disease is Kearns-Sayre syndrome.