[Coenzyme Q(10) treatment for one child with COQ6 gene mutation induced nephrotic syndrome and literature review].

Objective: To summarize the clinical manifestation and molecular characteristics of COQ6 mutation induced nephrotic syndrome, and to evaluate efficacy of CoQ(10) therapy. Method: Clinical data of the case with infantile nephrotic syndrome was summarized, including clinical manifestations, laboratory findings and family investigation. The patient received CoQ(10) 30 mg/(kg·d) therapy. Urine protein/creatinine ratio, serum albumin and creatinine were detected to assess the efficacy of the therapy. Result: (1) The 10 months old boy was presented with nephrotic level proteinuria and hypoalbuminemia. Extra-renal manifestations included cardiovascular abnormality, motor and mental retardation and unilateral ptosis. The patient had no consanguinity. A novel homozygous p. R360W mutation in COQ6 gene was identified and confirmed by next-generation sequencing and Sanger sequencing, respectively. Family analysis showed that homozygous p. R360W mutation in COQ6 gene was inherited from his parents. Missense p. R360W mutation was damaging by prediction online PolyPhen and SIFT software. After 2 months of CoQ(10) complementary therapy, the patient's urine protein/creatinine ratio declined from 7.2 to 1.3, and decreased further to 0.01 mg/mg with normal albumin level and renal function within 3 months. Nephropathy remission was maintained and growth retardation improved significantly during the last follow-up. Nevertheless, the patient manifested with sensorineural deafness at the age of 2 years. (2) There were 6 different mutations in coenzyme Q(10) biosynthesis monooxygenase 6 (COQ6) in 13 individuals from 7 families by homozygosity mapping in the whole world. Each mutation was linked to early-onset SRNS with sensorineural deafness. Renal biopsy revealed FSGS in 7 cases and DMS in 1 case. Other manifestations included ataxia, seizures, facial dysmorphism, nephrolithiasis and growth retardation. Four patients received CoQ(10) supplementation and responded to the treatment.
Conclusion: Renal disease caused by recessive COQ6 gene mutation was nephrotic syndrome. The patient benefited from early CoQ(10) complement and reached nephropathy remission.