Clinical whole-exome sequencing reveals a common pathogenic variant in patients with CoQ10 deficiency: An underdiagnosed cause of mitochondriopathy

[Background]: Primary CoQ deficiency occurs because of the defective biosynthesis of coenzyme Q, one of the key components of the mitochondrial electron transport chain. Patients with this disease present with a myriad of non-specific symptoms and signs, posing a diagnostic challenge. Whole-exome sequencing is vital in the diagnosis of these cases.[Case]: Three unrelated cases presenting as either encephalopathy or cardiomyopathy have been diagnosed to harbor a common pathogenic variant c.370G > A in COQ4. COQ4 encodes a key structural component for stabilizing the multienzymatic CoQ biosynthesis complex. This variant is detected only among East and South Asian populations.[Conclusions]: Based on the population data and our case series, COQ4-related mitochondriopathy is likely an underrecognized condition. We recommend including the COQ4 c.370G > A variant as a part of the screening process for mitochondriopathy in Chinese populations.This work was supported by the S.K. Yee Medical Foundation, Hong Kong