Absent or reduced splenic function

Aetiology

• Congenital asplenia: individual born without a spleen (rare)

• Anatomic hyposplenism: surgical removal of the spleen

• Functional hyposplenism: reduction of splenic function due to a pathological condition

  

Pathophysiology

Autosplenectomy: Spleen atrophy and degeneration due to multiple acute episodes of entrapment of large red cell volumes in the spleen, followed by splenic infarctions

Complications:

• Infection with encapsulated bacteria (asplenic sepsis)
  • Normally, encapsulated pathogens are opsonized with antibodies and then phagocytosed by splenic macrophages. Individuals with hyposplenia lack these specialized macrophages, so pathogens are able to spread and cause sepsis
  • H. influenzae, N. meningitidis, and S. pneumonia are the pathogens that most commonly cause asplenic sepsis.
• Infection with intraerythrocytic parasites (babiosis and malaria)
  • In a normal functioning spleen, the red pulp filters blood and removes old red blood cells; it causes phagocytosis of infected erythrocytes which helps to form a defence against intraerythrocytic parasites
• Vascular complications:
  • Patients with hyposplenia have increased risk of thrombotic events (stroke and MI). Commonly occur following surgical removal of the spleen.
• Adrenal haemorrhage (also known as Waterhouse-Friedrichsen syndrome and purpura fulminans)
  • Caused by infections with bacteria such as N. meningitidis, R. rickettsia and S. pneumoniae. Increased incidence in asplenia due to increased risk of infection