Approach to Anemia
Anemia is a hemoglobin below 12 g/dL in women or 13 g/dL in men, from underproduction, destruction, or loss of erythrocytes, never a final diagnosis in itself. The mean corpuscular volume (MCV) and reticulocyte count sort the differential, and management means treating the identified cause, iron or vitamin repletion, immunosuppression, or transfusion for symptomatic or severe disease.
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What this article covers
- Overview
Definition: anemia is a hemoglobin below 12 g/dL in women or below 13 g/dL in men, reflecting an insufficient number of erythrocytes to deliver oxygen to tissue.
- Epidemiology
Who is affected: iron deficiency is the most common cause worldwide, disproportionately affecting menstruating women, pregnant women, infants, and older adults with occult gastrointestinal blood loss.
- Risk factors
Nutritional and gastrointestinal: menorrhagia, occult gastrointestinal bleeding, celiac disease, prior gastrectomy or bariatric surgery, and poor dietary intake predispose to iron, B12, or folate deficiency.
- Pathophysiology
Production side: erythropoiesis depends on erythropoietin, made by the kidney in response to hypoxia, and on iron, cobalamin, and folate for hemoglobin and DNA synthesis; CKD causes relative…
- Clinical features
Symptom spectrum: dyspnea on exertion, fatigue, palpitations, and lightheadedness predominate; a slow chronic anemia is far better tolerated than a rapid drop to the same hemoglobin.
- Differential diagnosis
Iron deficiency anemia: microcytic with a high red cell distribution width (RDW), unlike thalassemia and anemia of inflammation, with a low ferritin (below 15 ng/mL) and a high TIBC that separate it from both.
- Diagnosis
What establishes the diagnosis: anemia is confirmed by a complete blood count (CBC) showing hemoglobin below 12 g/dL in women or below 13 g/dL in men; the specific cause is then established by the…
- Management
First, assess severity and stability: transfuse packed red blood cells for symptomatic anemia or hemodynamic instability regardless of the eventual cause, then pursue the mechanism-specific treatment.
- Complications
Untreated iron deficiency: worsening fatigue, high-output cardiac strain, and, in pregnancy, low birth weight and preterm delivery.
- Prognosis
Nutrient deficiency anemias: excellent once corrected and the cause of loss or malabsorption is treated, with recovery generally over weeks.
- Prevention
Iron deficiency: screen at-risk groups, including pregnant women and menstruating adolescents, and investigate iron deficiency in a man or postmenopausal woman for occult gastrointestinal bleeding…
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Related articles
- Iron deficiency anemia
Iron deficiency anemia is the most common anemia worldwide, a microcytic hypochromic anemia driven by chronic blood loss, poor intake or malabsorption, or increased iron demand. A ferritin below 15 ng/mL confirms depleted iron stores, and confirmed disease in men or postmenopausal women mandates bidirectional endoscopy to find an occult gastrointestinal source before treating with oral or intravenous iron.
- Anemia of chronic disease
Anemia of chronic disease, also called anemia of inflammation, is a normocytic normochromic anemia driven by hepcidin-mediated iron sequestration and cytokine blunting of erythropoiesis in patients with chronic infection, autoimmune disease, malignancy, or kidney disease. The iron-study pattern of low serum iron, low total iron-binding capacity, and normal-to-high ferritin distinguishes it from iron deficiency, and management centers on treating the underlying disease rather than iron supplementation.
- Hemolytic anemia: an overview
Hemolytic anemia is premature red cell destruction confirmed by a high reticulocyte count and LDH with low haptoglobin and high indirect bilirubin. The approach then classifies disease by smear findings and a direct antiglobulin test, separating immune from non-immune and inherited from acquired causes to direct treatment.
- Autoimmune hemolytic anemias
Autoimmune hemolytic anemia is antibody-mediated red cell destruction confirmed by a positive direct antiglobulin (Coombs) test, split into warm IgG disease with splenic clearance and spherocytes and cold agglutinin IgM disease with complement-mediated agglutination worse in the cold. Warm disease is treated with glucocorticoids first and cold agglutinin disease with cold avoidance and rituximab, and roughly half have an identifiable secondary cause that must be sought and treated.
- Pernicious anemia
Pernicious anemia is autoimmune atrophic gastritis that destroys gastric parietal cells and abolishes intrinsic factor production, causing vitamin B12 malabsorption, megaloblastic macrocytic anemia, and a potentially irreversible myelopathy and neuropathy. Diagnosis rests on a low or borderline B12 with an elevated methylmalonic acid, confirmed by anti-intrinsic factor antibody, and treatment is lifelong vitamin B12 replacement.
- Aplastic anemia
Aplastic anemia is an acquired or inherited hematopoietic stem cell disorder that produces pancytopenia with a hypocellular, fatty bone marrow and no dysplasia, blasts, or fibrosis. Diagnosis rests on marrow biopsy showing less than 25% cellularity with severity graded by the Camitta criteria, and treatment is allogeneic stem cell transplantation for young fit patients with a matched donor or antithymocyte globulin plus cyclosporine and eltrombopag for everyone else.
- Myelodysplastic syndromes
Myelodysplastic syndromes are clonal stem cell disorders producing ineffective hematopoiesis: a dysplastic, usually hypercellular bone marrow with peripheral cytopenias and a variable risk of transformation to acute myeloid leukemia. Diagnosis requires bone marrow biopsy showing dysplasia after excluding reversible mimics, risk is stratified with the IPSS-R, and treatment ranges from supportive transfusions and lenalidomide in lower-risk disease to hypomethylating agents and allogeneic transplant, the only cure, in higher-risk disease.
- Approach to Pancytopenia
Pancytopenia is the simultaneous reduction of hemoglobin, absolute neutrophil count (ANC), and platelets below the reference range, a sign of marrow failure, infiltration, or peripheral destruction rather than a diagnosis. The reticulocyte count and bone marrow biopsy separate the causes, and treatment combines transfusion or empiric antibiotics for the acute cytopenias with disease-specific therapy such as immunosuppression or transplantation for aplastic anemia.