The blood in systemic disorders.

* The high rate of proliferation required of the bone marrow renders it highly susceptible to the influence of external factors. * Anaemia is the most common haematological abnormality seen in systemic disorders. * In the anaemia of chronic disease, erythropoietin production is reduced and proliferation of erythroid progenitor cells is also impaired; this anaemia can generally be alleviated by correction of the underlying disease process. * The status of the endocrine system must always be considered in evaluation of a normocytic, normochromic anaemia. * Anaemia in infection can be due to host or parasite factors or to the treatment administered. * Anaemia due to malignant disease responds to erythropoietin therapy in many cases; failure to respond is a poor prognostic sign.