Severe renal tubulopathy and cholestasis due to BCS1L gene mutation of complex III: experience with high dose sodium bicarbonate therapy.

Defects of oxidative phosphorylation are a heterogeneous group of disorders which various clinical presentations. Isolated complex III deficiency is also a rare disorder in childhood. Recently patients with early liver failure, renal tubulopathy and encephalopathy due to the mutations in the BCS1L gene coding for a structural protein in complex III have been described. A ten-days-old female newborn was referred to our hospital because of intractable lactic acidosis, a lactate to pyruvate ratio of 34, an increase in blood alanine, alanineaminotransferase and aspartateaminotransferase levels, and generalized aminoaciduria were found. The tubulary phosphate reabsorbtion was reduced. Because of multisystem involvement, mitochondrial disease was suspected and the mutational analysis of the BCS1L gene revealed homozygote P99L mutation. As the patient was unresponsive to bicarbonate deficit, dichloroacetate and peritoneal dialysis, continuous intravenous sodium bicarbonate therapy with a dose up to 1.25 mEQ/Kg was started. The patient got well until the age of 7 months when she died of sepsis. It was stressed that a high dose of intravenous continuous sodium bicarbonate therapy could be an alternative treatment option in patients with severe acidosis resistant to dichloroacetate and peritoneal dialysis.