[Natural history of sickle cell anemia].

Sickle-cell anaemia is characterized by three categories of clinical signs: anaemia, vaso-occlusive phenomena and infective complications, which are described here according to age. The natural history of the disease can be divided into four periods: the neonatal period which is asymptomatic but important to organize an effective protection; the first 5 years of life are characterized by a high risk of mortality, a high level of morbidity due to severe infections, episodes of acute anaemia and painful crises typical of that age-group; the life of older children and adolescents is dotted with painful crises; it is in this period that degenerative tissue pathology begins; in adulthood, the acute episodes are less frequent, but multiple complications develop. Some of them (cerebral vascular accidents or lung diseases) may be fatal, while others are the source of chronic and disabling lesions, notably ocular, orthopaedic and renal lesions, which affect the functional prognosis. Pregnancy remains a high risk. There is, therefore, a striking contrast between the basic physiopathological mechanism (polymerization of haemoglobin S) and the various clinical manifestations which depend on the type of haemoglobin, on the social and sanitary conditions in each country and on other reasons which remain to be elucidated.