Monday, 6 July 2009

Splenomegaly: an approach to its causes (1)

The "causes of splenomegaly" is a must-know as you progress through medicine, and unfortunately the list is long. What we need, therefore, is an approach that is, quite literally, memorable. I'll take you through two, so that you can decide which one (if any?) is the more helpful. I'll give you the appropriate headings, and fill in a few of the commonest causes under each one. The entire list is even longer than the lists below, but that's not nearly so important as not missing a common cause in the midst of frantic memory trawling!

Splenomegaly I: By pathogenesis (credit: Harrison's 16th edn.)

1. Exageration of the spleen's functions (Spleen gets bigger due to hyperplasia)
  • Reticuloendothelial system hyperplasia (for increased removal of defective erythrocytes) - spherocytosis, haemoglobinopathies, nutritional anaemias
  • Immune hyperplasia secondary to infections - EBV, HIV, endocarditis, TB, histoplasmosis, malaria, leishmaniasis
  • Immune hyperplasia from disordered immunoregulation - rheumatoid arthritis, SLE, ITP, immune haemolytic anaemias, sarcoid
  • Extramedullary haemopoiesis - myelofibrosis, tumour infiltration by tumours/leukaemias/Gaucher's disease, marrow damage (e.g. toxins)
2. Abnormally high splenic blood flow (Spleen gets bigger due to housing more blood)
  • Cirrhosis
  • Hepatic/Portal/Splenic vein obstruction
  • Hepatic schisosomiasis/echinoccocosis
3. Infiltration (Spleen gets bigger from housing foreign material/cells)
  • Cellular - leukaemias, lymphomas, myeloproliferative syndromes, metastatic tumours, cysts
  • Non-cellular - amyloid, Gaucher's disease, mucopolysaccharides
4. Idiopathic (no one knows quite why the hell the spleen get's big)
  • Iron-deficiency anaemia, etc.

Tomorrow, we'll take the second approach.

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