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)
- 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.