Coenzyme Q10 (CoQ10) is an essential molecule produced within our body that exerts fundamental functions, including energy production within cells and protection against reactive oxidative species. A defect in CoQ10 production is associated with a group of diseases called primary CoQ10 deficiency.

COQ2 is one of the genes required to synthetize CoQ10 and it was the first to be found mutated in primary CoQ10 deficiency in 2006. COQ2 mutations lead to a reduction of CoQ10 levels in tissues. This condition is ultra-rare and the real prevalence is currently unknown. In the medical literature there are approximately 20 families described so far with a genetically defect in COQ2. However, considering that this condition was described recently, there might be more still unrecognized cases.

Clinical features
Patients with a defect in COQ2 may show extremely variable symptoms: in some patients the onset of the disease occurs soon after birth, with a very severe condition affecting multiple organs; in other patients, renal involvement is the main concern. Few individuals may manifest a neurological condition only later in life (6°-7° decade).

COQ2-associated CoQ10 deficiency is a genetic disorder due to mutations in COQ2. The disease is inherited in an autosomal recessive manner: this means that both copies of the COQ2 gene must be mutated in an individual to be affected, whereas heterozygotes (with only one mutated copy) are asymptomatic carriers and thus do not manifest the condition but are at risk of transmitting it. Parents of a patient are usually carriers of the mutations and they have a 25% chance to have other children affected. Therefore, a genetic counselling and testing at risk family members are crucial for these families.