Anaemia can be classified by underlying mechanism or red cell indices.

Based on Mechanism:

1. Decreased Production:
   • Nutritional deficiencies (e.g., iron, vitamin B12, folate).
   • Bone marrow disorders (e.g., aplastic anaemia, myelodysplastic syndrome).
   • Chronic diseases (e.g., chronic kidney disease, inflammatory conditions).
2. Increased Loss:
   • Acute or chronic blood loss (e.g., gastrointestinal bleeding, menorrhagia).
3. Increased Destruction:
   • Haemolytic anaemias (e.g., hereditary spherocytosis, sickle cell disease).

Based on Red Cell Indices:

1. Microcytic Anaemia (MCV < 80 fL):
   • Iron deficiency anaemia.
   • Thalassaemia.
   • Anaemia of chronic disease (sometimes).
2. Normocytic Anaemia (MCV 80–100 fL):
   • Acute blood loss.
   • Anaemia of chronic disease.
   • Haemolysis.
   • Mixed deficiency (e.g., iron and B12/folate).
3. Macrocytic Anaemia (MCV > 100 fL):
   • Vitamin B12 or folate deficiency.
   • Alcohol excess or liver disease.
   • Hypothyroidism.
   • Myelodysplastic syndromes.

Clinical Features:

1. General Symptoms:
   • Fatigue, pallor, shortness of breath, dizziness.
   • Palpitations, headaches.
2. Specific Signs:
   • Iron Deficiency: Koilonychia (spoon-shaped nails), angular stomatitis, glossitis.
   • B12 Deficiency: Neurological symptoms (e.g., paraesthesia, ataxia, cognitive impairment).
   • Haemolysis: Jaundice, dark urine, splenomegaly.

Investigations:

1. Full Blood Count (FBC):
   • Haemoglobin, haematocrit, mean cell volume (MCV), red cell distribution width (RDW).
2. Peripheral Blood Film:
   • Identifies abnormalities (e.g., target cells, schistocytes).
3. Iron Studies:
   • Ferritin, serum iron, transferrin saturation.
4. Vitamin Levels:
   • Serum B12, red cell folate.
5. Reticulocyte Count:
   • Low in decreased production; high in haemolysis or blood loss.
6. Special Tests:
   • Coombs test (autoimmune haemolysis), haemoglobin electrophoresis (thalassaemia, sickle cell).
   • Bone marrow biopsy (if underlying marrow pathology suspected).

Management:

General Principles:

1. Treat the Underlying Cause:
   • Address nutritional deficiencies, chronic diseases, or sources of blood loss.
2. Symptomatic Treatment:
   • Transfusions for severe or symptomatic anaemia.
3. Monitor and Reassess:
   • Regular monitoring of Hb levels and response to treatment.

Specific Treatments:

1. Iron Deficiency Anaemia:
   • Oral iron supplementation (e.g., ferrous sulphate); IV iron for intolerance or malabsorption.
   • Address sources of blood loss (e.g., gastrointestinal or menstrual).
2. Vitamin B12 Deficiency:
   • IM hydroxocobalamin or oral B12 supplements.
   • Treat underlying causes (e.g., pernicious anaemia).
3. Folate Deficiency:
   • Oral folic acid supplementation.
   • Exclude and treat coexisting B12 deficiency first.
4. Anaemia of Chronic Disease:
   • Manage underlying disease.
   • Consider erythropoiesis-stimulating agents (e.g., erythropoietin) in chronic kidney disease.
5. Haemolytic Anaemias:
   • Treat underlying cause (e.g., autoimmune haemolysis with corticosteroids).
   • Consider splenectomy or immunosuppressants if refractory.

Complications:

1. Cardiovascular:
   • Tachycardia, heart failure in severe cases.
2. Neurological:
   • Irreversible neuropathy in untreated B12 deficiency.
3. Chronic Fatigue:
   • Affects quality of life.

Key Exam Points for UKMLA:

1. Common Causes:
   • Recognise the causes of microcytic, normocytic, and macrocytic anaemia.
2. Diagnostic Approach:
   • Use FBC, MCV, and targeted tests (e.g., ferritin, B12) to identify the underlying cause.
3. Management Principles:
   • Focus on treating the underlying cause and monitoring response.
4. Red Flags:
   • Rapidly falling Hb, severe symptoms, or signs of haemolysis or bone marrow failure.