Anemia Overview: Types, Causes, Symptoms, and Management

What is anemia?

Anemia is defined as a condition in which the patient has reduced haemoglobin, hematocrit, or RBC count (healthy RBCs) Normal haemoglobin level and RBC counts are as follows:

• In men, the normal Hb level is 13.5-18 g/dl, and the RBC count is 4.7 to 6.1 cells/mcL.
• In women, the normal Hb level is 12–15 g/dl, and the RBC count is 4.2–5.4 cells/mcL.
• In children, the normal Hb level is 11 to 16g/dl, and the RBC count is 4 to 5.5 cells/mcL

The decreased count of RBCs can stem from three different routes:

• Loss of blood (hemorrhage, surgery, heavy menstrual bleeding, chronic gastrointestinal blood losses).
• Lack of RBC production (ineffective/defective erythropoiesis/lack of erythropoietin).
• High rates of blood cell destruction (sickle cell anaemia, hereditary spherocytosis, hereditary elliptocytosis, microangiopathic hemolytic anemia, macroangiopathic hemolytic anemia, etc.).

Though chronic and simple, anaemia can commonly lead to life-threatening complications.

Epidemiology

• The global distribution for anaemia is 2 billion, around 30% of the world's population.
• Women (especially pregnant, elderly, and women of reproductive age) tend to be affected more than males.
• In India, the prevalence of anemia is approximately 50%.
• Anemia is classified as a very common disease in India.
• It affects more than 10 million cases per year.

What are the signs and symptoms of anemia?

Symptoms:

• Headache
• Weakness
• Tiredness
• Lethargy
• Restless legs
• Shortness of breath
• Pica-an urge to eat non-dietary things

Signs:

• Tachypnea
• Hypotension
• Glossitis
• Tachycardia
• Decreased proprioception/vibration (in case of anaemia due to vitamin B12 deficiency)
• Pallor of the nail bed, mucous membranes, conjunctiva or palmar creases
• Koilonychia (in case of iron deficiency anaemia)
• Brittle nails

Also read: Chronic Kidney Disease (CKD): Overview, Causes, and Management 

What are the different types of anemia?

Iron deficiency Anemia

Iron deficiency anaemia is the most common type of anaemia, and the patient will have hypochromic and microcytic anaemia on the peripheral blood smear. It is caused by low levels of iron in the body (iron is an essential component of haemoglobin synthesis). Hence, decreased iron causes decreased haemoglobin production. 

The decreased iron content might be a result of one or more of the following factors:

• Blood loss (Acute/chronic)
• Decreased dietary intake of iron.
• Decreased iron absorption (celiac disease)
• Increased iron requirement (in pregnancy/illness)
• In children, increased intake of cow's milk (more than 24 ounces a day)

Diagnosis can be made by laboratory investigations with the following results:

• Low mean corpuscular volume (MCV< 80fL)
• Decreased RBC count
• Low/normal Reticulocytes
• Decreased Hemoglobin/Hematocrit
• Hypochromic, microcytic erythrocytes
• Anisocytosis (increased red cell distribution width)
• Increased total iron binding capacity
• Mentzer index (MCV/RBC count) greater than 13 suggests iron deficiency anemia, which differentiates it from thalassemia, in which the Mentzer index is less than 13.

Treatment for iron deficiency anemia

• Treatment mostly consists of treating the underlying cause and oral iron supplementation.
• Iron supplements are ideally taken before food, as iron absorption occurs efficiently in low gastric pH.
• Iron supplementation is taken for three months to restore the iron stores and then continued for another month after the hemoglobin level returns to normal.
• In cases of severe iron deficiency or intolerance to oral iron or malabsorption (post-gastrectomy or celiac disease), intravenous iron infusions are used.

Differential Diagnosis

• Lead poisoning
• Anemia of chronic disease
• Beta-Thalassemia

Complications

• High-output heart failure
• Increased infections
• Complications in pregnancy
• Developmental and growth problems in children

Also read: Understanding Addison's Disease: Causes, Symptoms, and Treatment 

Pernicious Anemia

Pernicious anaemia is a type of megaloblastic anaemia that occurs due to vitamin B12 deficiency due to a lack of intrinsic factors.

• Intrinsic factor (IF) is an intestinal glycoprotein contributing to vitamin B12 absorption. IF is produced from the gastric parietal cells. IF then binds with B12 and transports vitamin B12 to the terminal ileum, where it is absorbed.
• In the acidic gastric environment, dietary B12 is released from food carrier proteins via proteolysis and binds to haptocorrin, protecting B12 from degradation. Pancreatic proteases release B12 from haptocorrin in the small intestine, where it binds to IF produced by gastric parietal cells. The IFB12 complex binds to receptors in the terminal ileum and is endocytosed.
• If there's a lack of IF, there'll be a vitamin B12 deficiency. Since vitamin . B12 is an important constituent in RBC formation (DNA synthesis), leading to megaloblastic anaemia.

Presentation

• The patient will present with jaundice, glossitis, pallor, headache, fatigue, lethargy, and neurological manifestations.
• The earliest neurological manifestation would be peripheral neuropathy and subacute combined spinal cord degeneration at later stages.
• Pernicious anemia is associated with autoimmune disorders like type 1 diabetes, hypothyroidism, and vitiligo.

Laboratory Evaluations

Laboratory investigations for evaluation of pernicious anaemia include:

• CBC
• Folate level and cobalamin level
• Peripheral blood smear (mmacrocytic ovalocytes, anisopoikilocytosis and hypersegmented neutrophils)
• Serology for anti-parietal cell antibodies, anti-IF antibodies
• Bone marrow biopsy

Treatment

• Mild cases can be managed by oral vitamin B12 (1000–2000 micrograms) supplements. However, vitamin B12 (1000 micrograms) can be injected intramuscularly in cases of severe deficiency.

Differential Diagnosis

• Folate deficiency anaemia
• Drug-induced macrocytic anemia (methotrexate)
• Anemia due to alcohol abuse

Also read: Understanding Cardiac Tamponade: Causes, Symptoms, and Treatment

Sickle Cell Anemia

Sickle cell disease (SCD) is a group of blood disorders usually due to inherited defects of the beta-globin chain of haemoglobin. SCA is associated with malformed haemoglobin in RBCs. Haemoglobin comprises four globin chains (alpha and beta chains). Sickle cell anaemia occurs due to a mutation that replaces glutamine at the sixth position of the beta-globin chain with valine. This leads to rigid, elongated sickle-like-shaped polymers under certain circumstances (deoxygenated states). The symptoms become obvious by the age of 5–6 months.

Histopathology

• Howell-Jolly bodies: These are the remnants of DNA in the RBC in patients with autosplenectomy due to sickle cell disease.
• Target cell.

Laboratory Investigation

• In sickle cell anaemia, haemoglobin electrophoresis results show 80% sickle cell haemoglobin, 1% to 20% haemoglobin F, 2% to 4.5% haemoglobin A, and absence of 2 haemoglobin A.
• In the sickle cell anaemia trait, haemoglobin electrophoresis results show 40% or less sickle cell haemoglobin, normal haemoglobin F, increased haemoglobin A, and 60% or more hemoglobin A.

Treatment

Treatments focus on hydration, pain relief, and symptomatic management. As of now, there's no specific cure for sickle cell anaemia.

Complications

• Acute Chest syndrome
• Splenic sequestration crisis
• Acute stroke
• Aplastic crises
• Infections
• Priapism
• Avascular necrosis of the joints
• Renal complications (hyposthenuria, renal papillary necrosis) 

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