From GeneReviews Overview
Primary coenzyme Q10 (CoQ10) deficiency is usually associated with multisystem involvement, including neurologic manifestations such as fatal neonatal encephalopathy with hypotonia; a late-onset slowly progressive multiple-system atrophy-like phenotype (neurodegeneration with autonomic failure and various combinations of parkinsonism and cerebellar ataxia, and pyramidal dysfunction); and dystonia, spasticity, seizures, and intellectual disability. Steroid-resistant nephrotic syndrome (SRNS), the hallmark renal manifestation, is often the initial manifestation either as isolated renal involvement that progresses to end-stage renal disease (ESRD), or associated with encephalopathy (seizures, stroke-like episodes, severe neurologic impairment) resulting in early death. Hypertrophic cardiomyopathy (HCM), retinopathy or optic atrophy, and sensorineural hearing loss can also be seen.

From OMIM
Primary CoQ10 deficiency is a rare, clinically heterogeneous autosomal recessive disorder caused by mutation in any of the genes encoding proteins directly involved in the synthesis of coenzyme Q (review by Quinzii and Hirano, 2011). Coenzyme Q10 (CoQ10), or ubiquinone, is a mobile lipophilic electron carrier critical for electron transfer by the mitochondrial inner membrane respiratory chain (Duncan et al., 2009). The disorder has been associated with 4 major phenotypes, but the molecular basis has not been determined in most patients with the disorder and there are no clear genotype/phenotype correlations. The phenotypes include an encephalomyopathic form with seizures and ataxia (Ogasahara et al., 1989); a multisystem infantile form with encephalopathy, cardiomyopathy and renal failure (Rotig et al., 2000); a predominantly cerebellar form with ataxia and cerebellar atrophy (Lamperti et al., 2003); and Leigh syndrome with growth retardation (van Maldergem et al., 2002). The correct diagnosis is important because some patients may show a favorable response to CoQ10 treatment. Genetic Heterogeneity of Primary Coenzyme Q10 Deficiency See also COQ10D2 (614651), caused by mutation in the PDSS1 gene (607429) on chromosome 10p12; COQ10D3 (614652), caused by mutation in the PDSS2 gene (610564) on chromosome 6q21; COQ10D4 (612016), caused by mutation in the COQ8 gene (ADCK3; 606980) on chromosome 1q42; COQ10D5 (614654), caused by mutation in the COQ9 gene (612837) on chromosome 16q21; COQ10D6 (614650), caused by mutation in the COQ6 gene (614647) on chromosome 14q24; COQ10D7 (616276), caused by mutation in the COQ4 gene (612898) on chromosome 9q34; COQ10D8 (616733), caused by mutation in the COQ7 gene (601683) on chromosome 16p13; and COQ10D9 (619028), caused by mutation in the COQ5 gene (616359) on chromosome 12q24. Secondary CoQ10 deficiency has been reported in association with glutaric aciduria type IIC (MADD; 231680), caused by mutation in the ETFDH gene (231675) on chromosome 4q, and with ataxia-oculomotor apraxia syndrome-1 (AOA1; 208920), caused by mutation in the APTX gene (606350) on chromosome 9p13.  http://www.omim.org/entry/607426