In patients with homozygotic C4A deficiency, lymphomas were significantly more common than in other groups (12.50%, 4/32 in C4A deficient vs. 0.8%, 1/120 in controls OR = 17.00, 95%CI = 1.83–158.04, p = 0.007, Table 3). The gene discussed is C4A; the disease is lymphoma.