Medicine Medicine · Haematology · High Yield

Causes of Anaemia

Anaemia (Hb <130 g/L men, <120 g/L women) is classified by MCV into microcytic, normocytic, and macrocytic. Each size category has a distinct differential diagnosis.

✦ The Mnemonic

"TILSA Finds Microcytic; BLAND Macrocytic"

Microcytic (MCV <80): TILSA · Macrocytic (MCV >100): BLAND

T Thalassaemia Microcytic; normal/raised iron; raised HbA2 on electrophoresis
I Iron deficiency Most common cause worldwide; microcytic hypochromic; low ferritin
L Lead poisoning Microcytic; basophilic stippling; raised blood lead
S Sideroblastic anaemia Microcytic; ringed sideroblasts on bone marrow; causes include alcohol, INH
A Anaemia of chronic disease Normocytic or microcytic; low iron, low TIBC, raised ferritin
B B12/folate deficiency Macrocytic megaloblastic; hypersegmented neutrophils
L Liver disease Macrocytic; target cells; spur cells (in alcoholic liver disease)
A Alcohol Macrocytic; direct toxic effect on erythropoiesis; also depletes folate
N Neoplasm/myeloma Macrocytic or normocytic; plasma cells in myeloma; leukaemia
D Drugs / Dysthyroidism Macrocytic: methotrexate, hydroxyurea, zidovudine; hypothyroidism

📚 Clinical Breakdown

Iron studies interpretation: Iron deficiency = low serum iron, low ferritin, raised TIBC. Anaemia of chronic disease = low serum iron, raised ferritin (acute phase protein), low TIBC. The key distinction: ferritin is high in ACD and low in IDA — ferritin is the single most useful test.

B12 deficiency vs folate deficiency: both cause megaloblastic macrocytic anaemia with hypersegmented neutrophils. B12 deficiency also causes subacute combined degeneration of the spinal cord (dorsal and lateral columns) — folate does not. Always check B12 before treating with folate (giving folate to a B12-deficient patient can precipitate cord degeneration).

Haemolytic anaemia is normocytic: raised reticulocytes (haemopoietic response), raised bilirubin (unconjugated), raised LDH, low haptoglobin, raised urobilinogen. Causes: immune (warm or cold AIHA), hereditary (spherocytosis, elliptocytosis, G6PD, sickle cell), microangiopathic (TTP, HUS, DIC), mechanical (prosthetic valve).

Most common anaemia Iron deficiency (worldwide)
Ferritin in IDA Low
Ferritin in ACD High (acute phase protein)
B12 vs folate B12 causes cord disease; folate does not

⭐ Clinical Pearl

Sickle cell disease: HbS polymerises when deoxygenated, causing sickling and vaso-occlusion. The sickling crisis — acute painful crisis — is triggered by: cold, dehydration, infection, hypoxia. Management: analgesia (opioids), hydration, oxygen, antibiotics if infection. Annual transcranial Doppler screening identifies children at stroke risk (prophylactic exchange transfusion).

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