However, as underlined by Rothman et al [19], if activation of 5-HT2B receptors is necessary to produce valvular heart disease, other factors such as 5-HTT expression [29], hypoxia, inflammatory cytokines, and drugs, might also determine the individual susceptibility to develop the lesion, its anatomic location and its severity [17]. The gene discussed is SLC6A4; the disease is heart valve disorder.