Evaluation of renal function in children with mitochondrial respiratory chain complex defect: Usefulness of cystatin C

Aim: Mitochondrial disorders with respiratory chain complex defect are known to show a broad spectrum of clinical phenotypes, though their contribution to renal disease has not received much attention. The aim of this study was to evaluate renal function using different markers of the glomerular filtration rate (GFR) in children with mitochondrial respiratory chain complex (MRC) defects. Methods: Twenty-two patients with MRC I defect confirmed by biochemical enzyme assays using muscle tissue, were evaluated for renal function with diethylenetriaminepentaacetic acid (DTPA) renal scintigraphy, urine creatinine clearance, serum creatinine (Scr) and cystatin C (Cys C) levels. Results: All patients showed lower levels within normal range of Scr (0.4-0.7 mg/dL, mean 0.47 mg/dL), and with no significant correlation with DTPA-GFR. Cys C showed significant correlation with DTPA-GFR (p < 0.01) providing higher diagnostic accuracy than creatinine in patients with MRC defect. Conclusion: In mitochondrial disorder with MRC defect, Scr could not fully reflect renal function due to the relatively small body mass of patients. Considering the limited clinical availability of DTPA renal scintigraphy, Cys C should be taken as the first step to evaluate GFR in mitochondrial disorders.