Complement component 2 deficiency (C2D) is a genetic condition that affects the immune system. Signs and symptoms include recurrent bacterial infections and risk for a variety of autoimmune conditions. Infections can be very serious and are common in early life. They become less frequent during the teen and adult years. The most frequent autoimmune conditions associated with C2D are lupus (10-20%) and vasculitis. C2D is caused by mutations in the C2 gene and is inherited in an autosomal recessive fashion.