COQ2 nephropathy: a treatable cause of nephrotic syndrome in children
Nephrotic syndrome can be caused by a subgroup of mitochondrial diseases classified as primary coenzyme Q10 (CoQ10) deficiency. Pathogenic COQ2 variants are a cause of primary CoQ10 deficiency and present with phenotypes ranging from isolated nephrotic syndrome to fatal multisystem disease.
We report three pediatric patients with COQ2 variants presenting with nephrotic syndrome. Two of these patients had normal leukocyte CoQ10 levels prior to treatment. Pathologic findings varied from mesangial sclerosis to focal segmental glomerulosclerosis, with all patients having abnormal appearing mitochondria on kidney biopsy. In two of the three patients treated with CoQ10 supplementation, the nephrotic syndrome resolved; and at follow-up, both have normal renal function and stable proteinuria.
COQ2 nephropathy should be suspected in patients presenting with nephrotic syndrome, although less common than disease due to mutations in NPHS1, NPHS2, and WT1. The index of suspicion should remain high, and we suggest that providers consider genetic evaluation even in patients with normal leukocyte CoQ10 levels, as levels may be within normal range even with significant clinical disease. Early molecular diagnosis and specific treatment are essential in the management of this severe yet treatable condition.
KeywordsNephrotic syndrome Coenzyme Q10 deficiency COQ2 nephropathy Mitochondrial proliferation in podocytes Kidney pathology Ubiquinone
We would like to thank Dr. Carlos R. Ferreira at the National Institutes of Health for his contribution of expertise in CoQ10 deficiency-associated diseases and Dr. Mark Lovell at Colorado Children’s Hospital for his assistance with obtaining renal pathology. We would also like to thank the patients and families for their agreement to participate in our manuscript.
This study was supported by the National Institutes of Health (5T32GM007454 to IC) and (T32DK007662 to MS).
MS, IC, and CL generated ideal for case report. MS, IC, AS, AL, JG, CH, JVH, SH, and CL all participated in the clinical care of these patients. LF reviewed the renal pathology for all cases, assisted with interpretation of findings, and provided images for publication. MS wrote the first draft of this paper. All authors discussed the results and implications, commented on the manuscript at all stages, and approved the final manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
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