Plasmatic proinflammatory molecules (C-reactive protein, orosomucoid, RANTES, IL-6, IL-8, MCP-1, IL-1A, IL-1B, ET-1, IL-4, IL-10, TNFalpha, IFNgamma), hormones from the hypothalami-pituitary-adrenal axis (cortisol, ACTH), and hypothalamic peptids (arginine vasopressin, corticotrophin-releasing hormone) will be measured from SCD children treated or not with HU (20 treated children, 20 untreated children with a history of vaso-occlusive events, 20 asymptomatic children, and 20 healthy African controls).