Mitochondrial cytopathies and the kidney.

Mitochondrial cytopathies include a heterogeneous group of diseases that are characterized by impaired oxidative phosphorylation. Current evidence suggests that renal involvement is probably more frequent than originally suspected but remains subclinical in a significant number of patients or is underestimated due to the severity of other clinical manifestations. Until recently, these diseases were thought to develop primarily in pediatric patients but patients that become symptomatic only in adulthood are now well recognized. From a renal standpoint, many patients with severe systemic disease and several patients with oligo-symptomatic clinical pictures have tubular defects, ranging from isolated tubular wasting of electrolytes to complete forms of renal Fanconi syndrome. Aside from rare cases of tubulo-interstitial and cystic diseases, other patients present with glomerular diseases that correspond in the majority of cases to focal segmental glomerulosclerosis lesions. Two specific entities should be singled out, namely the 3243 A>G mutation in the gene encoding for the mitochondrial leucine tRNA because it represents the most frequent form of mitochondrial glomerulopathy, and defects in the biosynthesis of coenzyme Q10 because they represent one of the few treatable forms of mitochondrial cytopathies.