Fatal heart failure associated with CoQ10 and multiple OXPHOS deficiency in a child with propionic acidemia

The role of a secondary respiratory chain deficiency as an additional mechanism to intoxication, leading to development of long-term energy-dependent complications, has been recently suggested in patients with propionic acidemia (PA). We show for the first time a coenzyme Q10 (CoQ10) functional defect accompanied by a multiple organ oxidative phosphorylation (OXPHOS) deficiency in a child who succumbed to acute heart failure in the absence of metabolic stress. Quinone-dependent activities in the liver (complex I + III, complex II + III) were reduced, suggesting a decrease in electron transfer related to the quinone pool. The restoration of complex II + III activity after addition of exogenous ubiquinone to the assay system suggests CoQ10 deficiency. Nevertheless, we disposed of insufficient material to perform direct measurement of CoQ10 content in the patient's liver. Death occurred before biochemical diagnosis of OXPHOS deficiency could be made. However, this case highlights the usefulness of rapidly identifying CoQ10 defects secondary to PA since this OXPHOS disorder has a good treatment response which could improve heart complications or prevent their appearance. Nevertheless, further studies will be necessary to determine whether CoQ10 treatment can be useful in PA complications linked to CoQ10 deficiency.