HEMOGLOBINS S AND C: Drepanocytosis, the occurrence of sickle cells (drepanocytes) in the blood, is an inherited condition. Electrophoresis demonstrates hemoglobin SS in homozygous subjects who present the typical clinical features of severe hemolytic sickle-cell anemia. Heterozygous subjects have sickle-cell anemia trait, an asymptomatic condition associated with a 50% hemoglobin S and 50% hemoglobin C at electrophoresis. Hemoglobin S and C are transmitted by Mendelian inheritance. CARDIAC DISORDERS: Well-known, cardiac disorders occur in more than 82% of homozygous subjects while only 2% of heterozygous subjects are affected. Heart murmur, radiological cardiomegaly, or eletrocardiographic anomalies are often the only signs. There is a risk of fatal heart failure in children and neonates. Acute rheumatic fever or infectious endocarditis, particularly due to pneumococcal or Haemophilus influenzae infection, may trigger heart failure. CARDIAC ANOMALIES: Patients with sickle-cell anemia can develop an "anemic heart" expressed by an elevated cardiac output and systemic ejection volume at rest and a fall in arteriolar peripheral resistance. Patients who develop cor pulmonae have an elevated pulmonary pressure at exercise and experience venous occlusive events with a progressive reduction in the pulmonary vascular bed and development of a left-right shunt. Myocardiopathy leads to left ventricular dysfunction contrasting with the dilated right heart seen at echocardiography and rare cases of transmural infarction.