Coenzyme Q Deficiency Syndromes - Ubiquinone Deficiency

Diagnosis

Indications for Testing

Laboratory Testing

  • Serum creatinine kinase and lactic acid levels
    • Elevated in myopathic forms
    • Normal in cerebellar ataxic forms
  • Serum coenzyme Q testing – not useful in diagnosis (see Monitoring)

Histology

  • Muscle biopsy
    • Red, ragged fibers
    • Low fibroblast/muscle coenzyme Q levels

Differential Diagnosis

  • Mitochondrial diseases
  • Muscular dystrophy
  • Metabolic disorders
  • Friedreich ataxia

Monitoring

  • Serum coenzyme Q levels used for monitoring of therapy

Clinical Background

Coenzyme Q (ubiquinone) deficiency has been associated with a variety of diseases that include infantile as well as adult forms (uncommon).

Epidemiology

  • Incidence – rare
  • Age – most disorders present during infancy
  • Sex – M:F, equal

Inheritance

  • Autosomal recessive with variable phenotypes
    • Cerebellar ataxia – most common form 
    • Encephalomyopathy
    • Severe infantile multisystemic disease
    • Leigh syndrome
    • Isolated myopathy

Genetics

  • COQ2, PDSS1, PDSS2 mutations cause severe infantile forms

Pathophysiology

  • Coenzyme Q synthesized in the mitochondrial inner membrane and transports electrons in the mitochondria – essential for mitochondrial respiration
  • Coenzyme Q is also an antioxidant – prevents progression of lipid peroxidation in membranes
  • Affected patients have a deficiency in one of the enzymes needed to synthesize coenzyme Q

Clinical Presentation

  • Cerebellar ataxia  – ataxia, cerebellar atrophy, hypogonadism, seizures, developmental delay
  • Infantile forms
    • Musculoskeletal – generalized proximal muscle weakness, myopathy, myoglobinuria
    • Neurologic – seizures, progressive ataxia, cognitive impairment
    • Ophthalmologic – retinitis pigmentosa, optic nerve atrophy, nystagmus, myopia
    • Renal – nephritic syndrome causing renal failure
  • Leigh syndrome – necrotizing encephalopathy with vision loss, failure to thrive, and liver failure
  • Myopathy – muscle weakness; may have adult onset
  • Encephalomyopathy – myoglobinuria, brain involvement

Treatment

  • Oral coenzyme Q supplementation

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Creatine Kinase, Total, Serum or Plasma 0020010
Method: Quantitative Enzymatic

Confirm muscle involvement

Not specific for coenzyme Q deficiency

 
Creatine Kinase Isoenzymes 0020414
Method: Quantitative Enzymatic/Electrophoresis

Aid in determining the etiology of elevated total CK (differentiate between muscle and brain injury)

Components include CK-MM; CK-MB; CK-BB; and creatine kinase, total

Not specific for coenzyme Q deficiency

 
Lactic Acid, Plasma 0020045
Method: Enzymatic

Demonstrate muscle-damaging process

   
Coenzyme Q10, Total 0081119
Method: Quantitative High Performance Liquid Chromatography

Monitor replacement therapy in coenzyme Q deficiencies

Not useful in coenzyme Q deficiency diagnosis