complement component 5 deficiency

Complement component 5 deficiency is a rare genetic disorder that affects the immune system by impairing the production or function of the fifth complement component (C5). This impairment leads to a reduced ability to form the membrane attack complex, making affected individuals more susceptible to recurrent Neisserial infections, including meningococcal disease. The inherited form typically presents in the second decade of life. While precise prevalence data is not available, the condition is recognized as uncommon.

The clinical features of complement component 5 deficiency are centered on impaired immune function. Individuals with this condition consistently exhibit reduced circulating CH50 activity, decreased serum complement C5 levels, and are prone to recurrent meningococcal disease, which collectively serve as characteristic findings. Not all individuals experience every feature to the same extent, and severity can vary considerably.

Complement component 5 deficiency is caused by pathogenic variants in the C5 gene. Disruption of this gene leads to inadequate synthesis of the C5 protein or rapid depletion following its production, which compromises the formation of the membrane attack complex, an essential component of the innate immune response. The condition is inherited in an autosomal recessive pattern, meaning that an affected individual receives one defective copy of the gene from each parent, who are typically asymptomatic carriers.

Currently, management of complement component 5 deficiency focuses on supportive care and symptom management. Treatment is tailored to the individual and typically involves a multidisciplinary team to promptly address infections and monitor health status. Preventive measures, including early antibiotic intervention and vigilant monitoring for signs of infection, play a critical role. Genetic counseling is also recommended to help families understand inheritance patterns and to support decisions regarding family planning. Patients should discuss treatment options with their healthcare team to determine which therapies may be most appropriate for their specific situation.

With current standards of care, many individuals with complement component 5 deficiency effectively manage their susceptibility to infections, although clinical outcomes vary depending on factors such as infection severity and access to specialized care. The condition may progress, stabilize, or follow a variable course in different individuals, and outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with a genetic counselor and specialists familiar with immune disorders to discuss long-term management and care options.