Blood Cell Disorders

Also written as Hematology.

Blood cells are central to oxygen transport, immunity and clotting. In low‑resource settings, infections, nutritional deficiencies and hemoglobinopathies dominate. Rapid bedside assessment and simple tests guide urgent care.

Overview

Blood cells—erythrocytes, leukocytes and platelets—perform oxygen delivery, immune defense and haemostasis. Their morphology and count are altered by infections, nutritional deficiencies, genetic disorders and malignancy.

• Erythrocytes: red, biconcave, 120–140 days lifespan
• Leukocytes: white, 5–10×10^9/L, varied subtypes
• Platelets: anucleate, 150–400×10^9/L, 7–10 days

Key concepts

Clinical reasoning starts with the patient’s history, signs and simple investigations. In resource‑limited settings, the peripheral smear, full blood count (FBC) and basic chemistry are often the only data available.

• Thrombocytopenia: Platelets <150×10^9/L

Clinical relevance

Common causes in East Africa include malaria, HIV, TB, schistosomiasis, nutritional deficiencies (iron, folate, B12) and sickle cell disease. Prompt recognition prevents complications such as severe anaemia, sepsis and bleeding.

• Sickle cell: vaso‑occlusive crises, splenic sequestration

Investigations

• Peripheral smear: Shows morphology of cells; identifies sickle cells, malaria parasites, schistocytes, macrocytosis
• Full blood count: Quantifies Hb, WBC, platelets; guides transfusion, infection workup
• Reticulocyte count: Assesses marrow response; high in hemolysis, low in aplasia
• Serum ferritin: Elevated in iron overload, low in iron deficiency
• Peripheral eosinophil count: Suggests helminth infection or allergic disease
• Coombs test: Detects autoimmune hemolytic anemia

Management

Treat the underlying cause first, then provide supportive care. In emergencies, transfuse packed cells or platelets, give antibiotics for sepsis, and manage pain in sickle cell crises.

• Severe thrombocytopenia: platelet transfusion if bleeding or <20×10^9/L

Often confused with

Certain conditions mimic blood cell disorders; recognising subtle differences is key.

• Aplastic anemia vs hypersplenism: pancytopenia with splenomegaly vs isolated cytopenia

Where results can mislead

Lab values can be falsely normal or abnormal due to technical issues or physiological states.

• Platelet count falsely low in pseudothrombocytopenia (clotting in EDTA tube)

Exam pearls

Examiners test clinical reasoning: history, examination, differential, investigations and urgent management.

• Order FBC first; if abnormal, proceed to smear and targeted tests

Common mistakes

Students often focus on definitions rather than clinical context.

• Overlooking splenic sequestration in sickle cell

Questions an examiner may ask

• A 25‑year‑old woman presents with fever, splenomegaly and pancytopenia. What is the next best investigation? — Peripheral smear to look for malaria parasites or schistocytes; if negative, consider aplastic anemia or hypersplenism.
• A patient with sickle cell disease develops sudden abdominal pain and a drop in Hb. What is the likely diagnosis and immediate management? — Splenic sequestration; urgent splenectomy or transfusion if haemodynamic instability.
• A child has pallor, fatigue and a low Hb of 8 g/dL. Ferritin is 30 ng/mL. What is the most likely cause and first treatment? — Iron deficiency; start oral ferrous sulfate and dietary advice.
• A 60‑year‑old man with HIV presents with fever and thrombocytopenia (platelets 25×10^9/L). What is the first step in management? — Start broad‑spectrum antibiotics for possible sepsis and consider platelet transfusion if bleeding.
• A patient with a history of malaria presents with jaundice and a high reticulocyte count. What is the likely mechanism? — Hemolytic anaemia due to parasite‑induced red cell destruction.
• A 30‑year‑old man has a normal Hb but a WBC of 2×10^9/L. What is the most likely cause and next test? — Neutropenia; check for viral infections (EBV, CMV) and consider bone marrow aspirate if persistent.
• A patient with a known hemoglobinopathy presents with sudden drop in Hb and abdominal pain. What complication should you suspect and how to confirm? — Splenic sequestration; confirm with ultrasound showing enlarged spleen and rapid drop in Hb.
• A 45‑year‑old woman with chronic fatigue has a platelet count of 50×10^9/L. What is the most common reversible cause in this setting? — Iron deficiency; treat with iron and repeat count.

When to seek help

• Severe anaemia with tachycardia or hypotension
• Uncontrolled bleeding
• Severe thrombocytopenia with petechiae
• High fever with rigors and neutropenia

Quick questions

What is the most common cause of anaemia in East Africa?

Malaria and nutritional deficiencies, especially iron deficiency.

How do you differentiate iron deficiency from thalassemia on a smear?

Iron deficiency shows microcytosis with hypochromia and low ferritin; thalassemia shows target cells and normal ferritin.

Why is platelet transfusion avoided in dengue?

Because of the risk of volume overload and worsening capillary leak; supportive care is preferred unless active bleeding.