Increased demands not met by normal dietary intake occur worldwide during pregnancy and infancy.
Malabsorption can occur with celiac disease or after gastrectomy (Chapter 15).
Fig. 12.10 Irondeficiencyanemia—peripheralbloodsmear.Notetheincreasedcentralpallorofmostoftheredcells.Scattered,fullyhemoglo-binizedcells,fromarecentbloodtransfusion,standoutincontrast.(Courtesy of Dr. Robert W. McKenna, Department of Pathology, University of Texas South-western Medical School, Dallas,Texas.)
Regardless of the cause, iron deficiency develops insidiously. Iron stores are depleted first, marked by a decline in serum ferritin and the absence of stainable iron in the bone marrow. These changes are followed by a decrease in serum iron and a rise in the serum transferrin. Ultimately, the capacity to synthesize hemoglobin, myoglobin, and other iron-containing proteins is diminished, leading to microcytic anemia, impaired work and cognitive performance, and even reduced immunocompetence.
Clinical Features. In most instances iron deficiency anemia is mild and asymptomatic. Nonspecific manifestations, such as weakness, listlessness, and pallor, may be present in severe cases. With long-standing anemia, abnormalities of the fingernails, including thinning, flattening, and “spooning,” may appear. A curious but characteristic neurobehavioral complication is pica, the compunction to consume nonfoodstuffs such as dirt or clay.
In peripheral smears, red cells are microcytic and hypo-chromic (
Fig. 12.10 ). Diagnostic criteria include anemia, hypochromic and microcytic red cell indices, low serum ferritin and iron levels, low transferrin saturation, increased total iron-binding capacity, and, ultimately, response to iron therapy. For unclear reasons, the platelet count often is elevated. Erythropoietin levels are elevated, but the marrow response is blunted by the iron deficiency; thus, marrow cellularity usually is only slightly increased.
Persons often die with iron deficiency anemia, but virtually never of it. An important point is that in well-nourished persons, microcytic hypochromic anemia is not a disease but rather a symptom of some underlying disorder.
Often referred to as the anemia of chronic disease, anemia associated with chronic inflammation is the most common form of anemia in hospitalized patients.
It superficially resembles the anemia of iron deficiency but arises instead from the suppression of erythropoiesis by systemic inflammation. It occurs in a variety of disorders associated with sustained inflammation: • Chronic microbial infections, such as osteomyelitis, bacterial endocarditis, and lung abscess http://ebooksmedicine.net
Chronic immune disorders, such as rheumatoid arthritis and regional enteritis
Neoplasms, such as Hodgkin lymphoma and carcinomas of the lung and breast
The anemia of chronic inflammation stems from high levels of plasma hepcidin, which blocks the transfer of iron to erythroid precursors by downregulating ferroportin in macrophages. The elevated hepcidin levels are caused by proinflammatory cytokines such as IL-6, which increase hepatic hepcidin synthesis. In addition, chronic inflammation blunts erythropoietin synthesis by the kidney, lowering red cell production by the marrow. The functional advantages of these adaptations in the face of systemic inflammation are unclear; they may serve to inhibit the growth of iron-dependent microorganisms or to augment certain aspects of host immunity.