The persistence (or the recurrence) of intravascular hemolysis is observed only in few conditions: (i) Japanese patients carrying a rare polymorphism of C5 [17], (ii) patients with an increased eculizumab turnover requiring extra-dosage (pharmacokinetic breakthrough) [18], and (iii) patients who occasionally experience transient episodes of intravascular hemolysis because of massive complement activation during infections or inflammatory disorders (pharmacodynamic breakthrough) [18–21]. The gene discussed is C5; the disease is hemolysis.