[Erythropoiesis: Physiology, pathophysiology, and algorithm for classification of the type of anemia].

Erythropoiesis is a continuous process that replaces 1% of all erythrocytes per day. To keep the erythrocyte count within stable limits about 3 million cells/s must be renewed. This enormous turnover requires folic acid and vitamin B12 for proper cell differentiation and iron for sufficient haemoglobin synthesis. In particular, iron metabolism underlies a precise regulation which may be disturbed by chronic bleeding, inflammatory disease or impaired dietary intake. If the loss of red blood cells due to physiological aging or bleeding is not balanced by sufficient erythropoiesis in the bone marrow, anaemia will develop. For the classification of various types of anaemia, a well-established algorithm has been proven useful. This algorithm addresses basic questions such as erythrocyte volume, the underlying mechanism, e.g. whether too many cells are destroyed or new cells are not sufficiently generated, and finally aims to define the main causes for the above identified disturbance of erythropoiesis.