Mitral prolapse is frequently encountered in association with other manifestations of mesenchymal dysplasia (skin hyperelastosis, joint hypermobility, dislocations, etc.) and occasional bleedings. Of 35 cases reported, 17 had petechiae and ecchymoses, 1 had hematuria, the rest suffered from bleedings: nasal (22 cases), profuse menstrual (19 cases), long-term extraction and cut bleedings (9 cases), gastrointestinal (3 cases). Hemorrhages of different sites often occurred in combination. Hemostatic investigations revealed: platelet aggregation dysfunction, Willebrand syndrome, end coagulation disturbances, lack or anomalies of factors VII, X and II (14, 17, 12 and 4 patients, respectively).