The association of Down syndrome with mannose-binding lectin (MBL)-deficiency, recurrent infections and vasculitis has not been reponed. We repon a 30 year-old female with Down-syndrome associated with MBL-deficiency with the genotype LXA/HYD, IgG-deficiency, recurrent uro-genital infections, cutaneous vasculitis, G20.210A prothrombin mutation, deep venous thrombosis, and pulmonary embolism. MBL-deficiency in combination with IgG deficiency might have favored the development of recurrent uro-genital infections. Immunodeficiency might be also involved in the pathogenesis of cutaneous vasculitis. Deep venous thrombosis and pulmonary embolism were attributed to the genetically determined prothrombotic state and intake of oral contraceptives.