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Anaemia Overview

Table of Contents

  • Introduction
  • Clinical Features
  • Microcytic Anaemias
  • Normocytic Anaemias
  • Macrocytic Anaemias
  • Key Points
  • References
  • Related Notes
  • Test Yourself

Introduction

  • Anaemia is a common condition characterized by reduced haemoglobin, impairing oxygen delivery to tissues.
  • Normal haemoglobin levels: Women 115-165 g/L; Men 130-180 g/L (due to larger body size).
  • Classified by mean corpuscular volume (MCV):
  • Microcytic: MCV < 80 fL
  • Normocytic: MCV 80-100 fL
  • Macrocytic: MCV > 100 fL

Clinical Features

History

  • Symptoms: pallor, fatigue, breathlessness, dizziness, palpitations, cold extremities.
  • Important history: dietary intake, blood loss (e.g., menorrhagia), malabsorption (gastrectomy, coeliac), family history of haematological disorders, GI bleeding (black tarry stools), chronic diseases (cardiac, renal, hepatic).

Examination

  • Pallor (general/conjunctival).
  • Rapid/irregular heartbeat.
  • Hepatosplenomegaly (consider lymphoma, leukaemia).
  • Pelvic or rectal exam to assess blood loss if indicated.

Microcytic Anaemias (MCV < 80 fL)

  • Caused by impaired haemoglobin synthesis resulting in smaller, hypochromic RBCs.
  • Common causes:
  • Iron deficiency anaemia (most common)
  • Sideroblastic anaemia (defective protoporphyrin synthesis)
  • Thalassaemia (inherited globin chain mutations)

Iron Deficiency Anaemia

  • Causes: blood loss, increased demand (childhood, pregnancy), malnutrition.
  • Symptoms: fatigue, palpitations, pica (ice, dirt).
  • Investigations: low serum iron, low transferrin saturation, low ferritin, high TIBC.

Sideroblastic Anaemia

  • Congenital or acquired (alcohol, lead, B6 deficiency).
  • Iron accumulates in mitochondria → ringed sideroblasts on smear.
  • Iron studies show iron overload.

Thalassaemia

  • Autosomal recessive mutations in alpha or beta globin genes.
  • Clinical: from mild trait to severe transfusion-dependent disease.
  • Common in Mediterranean, Africa, Asia.
  • Investigations: low MCV, normal/high ferritin, abnormal haemoglobin electrophoresis.

Normocytic Anaemias (MCV 80-100 fL)

  • Normal RBC size; causes include haemolysis or decreased RBC production.
  • Reticulocyte count distinguishes haemolysis (high) vs underproduction (low).
  • Usually normochromic.

Haemolytic Anaemias

  • Extravascular haemolysis: RBC destruction mainly in spleen (more common).
  • Intravascular haemolysis: RBC destruction in circulation (less common).
  • Includes: hereditary spherocytosis, sickle cell anaemia, paroxysmal nocturnal haemoglobinuria (PNH), G6PD deficiency, immune haemolytic anaemia, microangiopathic haemolytic anaemia.

Macrocytic Anaemias (MCV > 100 fL)

  • Divided into megaloblastic (impaired DNA synthesis) and non-megaloblastic types.

Megaloblastic Anaemia

  • Causes: folate deficiency, vitamin B12 deficiency.
  • Folate deficiency: elevated homocysteine, normal methylmalonic acid.
  • Vitamin B12 deficiency: elevated homocysteine and methylmalonic acid.
  • B12 deficiency often due to pernicious anaemia (autoimmune destruction of gastric parietal cells → intrinsic factor deficiency).

Non-Megaloblastic Anaemia

  • Causes: alcoholism, hypothyroidism, reticulocytosis, certain drugs.
  • Normal homocysteine and methylmalonic acid levels.

Summary Tables

Microcytic Anaemias

Condition Serum Iron Ferritin TIBC
Iron deficiency Low Low High
Anaemia of chronic disease Low High Low
Sideroblastic anaemia High High Low

Normocytic Anaemias - Haemolysis Overview

Condition Intravascular Extravascular Reticulocyte count Uric acid
Hereditary spherocytosis No Yes Increased Increased
Sickle cell anaemia Yes Yes Increased Increased
Paroxysmal nocturnal haemoglobinuria Yes No Normal Increased
G6PD deficiency Yes No Increased Increased
Immune haemolytic anaemia (IgM) Yes No Increased Increased
Immune haemolytic anaemia (IgG) No Yes Increased Increased
Microangiopathic haemolytic anaemia Yes No Increased Increased

Macrocytic Anaemias

Condition Homocysteine Methylmalonic Acid
Folate deficiency ↑ Normal
Vitamin B12 deficiency ↑ ↑
Non-megaloblastic N/A N/A

Key Points

  • Anaemia is defined by low haemoglobin levels.
  • Classified by RBC size into microcytic, normocytic, and macrocytic.
  • Symptoms include fatigue, breathlessness, pallor, palpitations, dizziness, and cold extremities.
  • Iron studies and reticulocyte count are essential for diagnosis and classification.
  • Serum methylmalonic acid and homocysteine help differentiate macrocytic anaemias.

References

  • Bruno de Benoist. Worldwide prevalence of anaemia 1993-2005. 2008.
  • NICE Clinical Knowledge Summary. Anaemia - Iron Deficiency.
  • Geeky Medics. Reference Ranges.
  • Mayo Clinic Staff. How is anaemia diagnosed?
  • Hematology-Oncology Associates of CNY. Anaemia Clinical Presentation.
  • Others as per source.

Test Yourself

  • [Link to clinical questions and self-assessment on anaemia]

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