Long-term, regular prophylaxis with FVIII concentrates, aimed at preventing in particular bleeding into joints to avoid or delay the development of hemophilic arthropathy, thus enabling an active lifestyle and satisfactory quality of life, has been recognized since the 1990s as the standard of care in patients with severe hemophilia A [5,6,7] and, more recently, even in those with moderate forms with relevant bleeding manifestations [4,8]. The gene discussed is F8; the disease is hemophilia A.