Description
Anemia is a condition where there are either too few red blood cells or too little hemoglobin in them. The capacity of the blood to transfer oxygen to the body's tissues will be reduced if you have too few or malformed red blood cells, not enough hemoglobin, or both. Hemoglobin is required to carry oxygen. This causes symptoms like weakness, exhaustion, lightheadedness, and shortness of breath, among others. Age, sex, elevation of habitation, smoking habits, and pregnancy status all affect the ideal haemoglobin concentration required to meet physiologic needs. Nutritional deficiencies, especially iron deficiency, as well as haemoglobinopathies, infectious illnesses like malaria, and vitamin B12, folate, and vitamin A deficiencies are the most frequent causes of anemia.
Summary Listen
- Anemia is defined as hemoglobin levels below 13.6 g/dL in males and 12 g/dL in females, and is classified based on pathophysiology (diminished production or increased destruction) and RBC size (MCV: microcytic, normocytic, macrocytic). Diminished production results in low reticulocyte counts, while increased destruction leads to elevated reticulocyte counts. Reticulocyte count is a marker of bone marrow function, also elevated in acute blood loss or after replacing deficiencies like iron.
- When evaluating anemia, begin with a platelet count and peripheral smear examination. A reticulocyte count distinguishes between underproduction (low reticulocytes) and increased destruction (high reticulocytes). Low reticulocyte counts prompt assessment of MCV to further categorize anemia by RBC size.
- Microcytic anemia (low MCV) warrants an iron profile, including ferritin and transferrin saturation. Low ferritin and transferrin saturation indicate iron deficiency, which is treated with oral or parenteral iron. Thalassemia should be considered when the iron profile is atypical, requiring hemoglobin electrophoresis for diagnosis.
- Normocytic anemia (normal MCV) also necessitates an iron profile to rule out iron deficiency. If iron deficiency is not present, consider anemia of chronic disease or inflammation, commonly associated with conditions like rheumatoid arthritis, inflammatory bowel disease, chronic infections, malignancies, and chronic kidney disease.
- Macrocytic anemia (high MCV) prompts evaluation of B12, folate, TSH, and alcohol history. B12 or folate deficiencies are common causes, but hypothyroidism, chronic liver disease, and alcohol abuse should also be considered. If B12 levels are borderline, consider testing methylmalonic acid and homocysteine.
- Hemolytic anemia involves increased RBC destruction, resulting in high reticulocyte counts, elevated unconjugated bilirubin, and increased LDH. Haptoglobin levels are decreased. Intravascular hemolysis can lead to hemoglobinuria and hemosiderinuria. Extravascular hemolysis often causes splenomegaly. Physical exam is important to check for lymph nodes, liver and spleen.
- Pancytopenia (reduction in all three cell lines) usually indicates bone marrow dysfunction, often requiring bone marrow biopsy. However, B12 deficiency, hypersplenism (seen in liver cirrhosis), acute alcohol intoxication, tuberculosis, and sepsis should be considered. Anemia with thrombocytopenia can be caused by microangiopathic hemolytic anemia, mechanical valves, autoimmune processes, or hypersplenism.
- MCV (mean corpuscular volume) is crucial for anemia diagnosis. MCH (mean corpuscular hemoglobin) measures the amount of hemoglobin in one RBC, and MCHC (mean corpuscular hemoglobin concentration) measures the proportion of each cell taken up by hemoglobin. RDW (RBC distribution width) indicates variation in RBC size, and it is high in iron deficiency, B12/folate deficiency, and mixed anemias.
- Iron deficiency anemia is the most common cause of anemia worldwide, caused by GI loss, diet deficiency, malabsorption. Symptoms are weakness, fatigue, shortness of breath, palpitations. Iron profile findings include low serum iron, low transferrin saturation, and high TIBC. Treat by addressing source of bleeding, and replenishing iron. Oral supplements cause discomfort so use parenteral if needed.
- Anemia of chronic disease, common in hospitalized patients, is associated with chronic diseases and inflammation. In chronic kidney disease, erythropoietin production is reduced. Treatment is targeted at the underlying cause, erythropoietin.
- B12 deficiency causes macrocytic anemia and megaloblastic blood smear with hypersegmented neutrophils. It results from dietary deficiency, pernicious anemia, abdominal surgeries, bowel disease, PPI use. Present with neurological symptoms or dementia. Diagnosis with B12 serum level.
- Folic acid deficiency, also leading to megaloblastic anemia, can occur in pregnant women and alcoholics. Always rule out B12 deficiency before treatment.
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About the Speakers
Dr Gautam Panduranga
MD in General Medicine, Osmania Medical College MRCP, UK MD in Internal Medicine, USA American Board Certified Internal Medicine
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