Protein-calorie malnutrition (PCM) is usually found in children, the elderly, patients suffering from neoplasia or chronic disease, patients undergoing chemotherapy, or even patients under parenteral nutrition. PCM presents a wide spectrum of signs and symptoms that are a result of not only the cause(s) that led to malnutrition, but also of the different degrees of protein or carbohydrate deficiency. Here we present data obtained from observational and experimental epidemiological studies that suggest that malnourished individuals frequently present a greater susceptibility to infection with high morbidity and mortality indices. Data both found in literature and obtained by our group evidence that malnutrition modifies the organism's defence processes, impairing lympho-haematopoietic organs and modifying immune response. The haematological alterations in malnutrition, such as leucopoenia and hypoplasia, are described, with an emphasis on the results in experimental protein malnutrition obtained by our group. In particular, the structural and ultra-structural alterations of bone marrow, spleen and thymus; functional alterations such as the reduction of cell migration and spreading, phagocytosis, bactericidal and fungicidal activity as well as alterations in the production of reactive oxygen species are discussed. The implications of modifications of the haemopoietic environment in malnutrition states are still obscure, however, they seem to be responsible for inefficient haemopoiesis, especially inefficient myelopoiesis, and they seem to be irreversible over the short-term.
Malnutrition; bone marrow; marrow hypoplasia; anaemia; leucopoenia