ELDER TIP With age, vitamin B12 absorption may also diminish, resulting in reduced erythrocyte mass and decreased hemoglobin (Hb) levels and hematocrit (HCT).
Pernicious anemia primarily affects people of northern European ancestry. It’s rare in children and infants. Onset typically occurs after age 35, and incidence increases with age. It affects about 2% of people older than age 60.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Sickle cell anemia:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Sickle cell anemia results from homozygous inheritance of the gene that produces HbS (chromosome 11). It's inherited as an autosomal recessive trait. Heterozygous inheritance of this gene results in sickle cell trait, a condition that usually produces no symptoms. (See Sickle cell trait.) Sickle cell anemia is most common in tropical Africans and in people of African descent; about 1 in 10 American blacks carries the abnormal gene. However, sickle cell anemia also appears in other ethnic populations, including people of Mediterranean or East Indian ancestry.
If two parents who are both carriers of sickle cell trait (or another hemoglobinopathy) have offspring, each child has a 25% chance of developing sickle cell anemia. (See Inheritance patterns in sickle cell anemia, page 22.) Overall, 1 in every 400 to 600 black children has sickle cell anemia. The defective HbS-producing gene may have persisted because, in areas where malaria is endemic, the heterozygous sickle cell trait provides resistance to malaria and is actually beneficial.
The abnormal HbS found in such patients' RBCs become insoluble whenever hypoxia occurs. As a result, these RBCs become rigid, rough, and elongated, forming a crescent or sickle shape. (See Comparing normal and sickled red blood cells.) Such sickling can produce hemolysis (cell destruction). In addition, these altered cells tend to pile up in capillaries and smaller blood vessels, making blood more viscous. Normal circulation is impaired, causing pain, tissue infarctions, and swelling. Such blockage causes anoxic changes that lead to further sickling and obstruction.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Sideroblastic anemias:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Hereditary sideroblastic anemia appears to be transmitted by X-linked inheritance, occurring mostly in young males; females are carriers and usually show no signs of this disorder.
The acquired form may be secondary to ingestion of or exposure to toxins, such as alcohol and lead, or to certain drugs. It can also occur as a complication of other diseases, such as rheumatoid arthritis, lupus erythematosus, multiple myeloma, tuberculosis, and severe infections.
The primary acquired form, known as refractory anemia with ringed sideroblasts, is most common in elderly people. It’s commonly associated with thrombocytopenia or leukopenia as part of a myelodysplastic syndrome.
In sideroblastic anemia, normoblasts fail to use iron to synthesize Hb. As a result, iron is deposited in the mitochondria of normoblasts, which are then termed ringed sideroblasts.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Iron deficiency anemia:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Iron deficiency anemia may result from:
❑ inadequate dietary intake of iron (less than 1 to 2 mg/day), such as in prolonged unsupplemented breast-feeding or bottle-feeding of infants or during periods of stress such as rapid growth in children and adolescents
❑ iron malabsorption, such as in chronic diarrhea, partial or total gastrectomy, chronic diverticulosis, and malabsorption syndromes, such as celiac disease and pernicious anemia
❑ blood loss secondary to drug-induced GI bleeding (from anticoagulants, aspirin, and steroids) or due to heavy menses, hemorrhage from trauma, GI ulcers, esophageal varices, or cancer
❑ pregnancy, which diverts maternal iron to the fetus for erythropoiesis
❑ intravascular hemolysis-induced hemoglobinuria or paroxysmal nocturnal hemoglobinuria
❑ mechanical erythrocyte trauma caused by a prosthetic heart valve or vena cava filters.
A common disease worldwide, iron deficiency anemia affects 10% to 30% of the adult population of the United States. It occurs most commonly in premenopausal women, infants (particularly premature or low-birth-weight neonates), children, and adolescents (especially girls). Persons who are at increased risk for iron deficiency include those of low socioeconomic status who don’t get a well-balanced diet that includes iron-rich foods.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Aplastic anemias:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Aplastic anemias usually develop when damaged or destroyed stem cells inhibit red blood cell (RBC) production. Less commonly, they develop when damaged bone marrow microvasculature creates an unfavorable environment for cell growth and maturation. About one-half of such anemias result from drugs (antibiotics and anticonvulsants), toxic agents (such as benzene and chloramphenicol), or radiation. The rest may result from immunologic factors (unconfirmed), severe disease (especially hepatitis), or preleukemic and neoplastic infiltration of bone marrow.
Idiopathic anemias may be congenital. Two such forms of aplastic anemia have been identified: Congenital hypoplastic anemia (Blackfan-Diamond anemia) develops between ages 2 and 3 months; Fanconi’s syndrome, between birth and age 10. In Fanconi’s syndrome, chromosomal abnormalities are usually associated with multiple congenital anomalies, such as dwarfism, and hypoplasia of the kidneys and spleen. In the absence of a consistent familial or genetic history of aplastic anemia, researchers suspect that these congenital abnormalities result from an induced change in the fetus’development.
Incidence is 0.6 to 6.1 cases per 1 million people. There is no racial predilection.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Iron Deficiency Anemia:
Iron Deficiency Anemia - epidemiology
(The 5-Minute Pediatric Consult)
- Leading cause of anemia among infants and children in the US
- Most commonly seen in children ages 9 months to 3 years and in teenage girls
Iron Deficiency Anemia - prevalence
- Prevalence is variable depending on socioeconomic status, availability of iron-fortified formulas, prevalence and duration of breastfeeding, and the way that iron deficiency is defined.
- Prevalence of iron deficiency anemia is generally between 1% and 5% of children in the US.
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Source: The 5-Minute Pediatric Consult, 2008
About prevalence and incidence statistics:
The term 'prevalence' of Iron deficiency anemia usually refers to the estimated population
of people who are managing Iron deficiency anemia at any given time.
The term 'incidence' of Iron deficiency anemia refers to the annual diagnosis rate,
or the number of new cases of Iron deficiency anemia diagnosed each year.
Hence, these two statistics types can differ:
a short-lived disease like flu can have high annual incidence but low prevalence,
but a life-long disease like diabetes has a low annual incidence but high prevalence.
For more information see about prevalence and incidence statistics.
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