Asplenia/Hyposplenia

Basics

Asplenia is the absence of the spleen due to either a congenital anomaly or a surgical procedure.
Hyposplenia is the reduced or absent function of the spleen, impairing the capacity to prevent bacterial infections.

The spleen is a major component of the reticuloendothelial system; it is important both for antibody synthesis and for clearance of opsonized organisms by phagocytosis.
Antibody-mediated phagocytosis is the primary mechanism to destroy encapsulated microbes, such as pneumococcus, meningococcus, and Haemophilus.
In the absence of the spleen’s phagocytic pathway, the polysaccharide-rich capsules of these bacteria protect them from destruction and permit them to effect systemic bacterial infection that may lead to overwhelming sepsis.
For patients <4 years of age in whom few alternate routes of bacterial clearance exist, significant pathology can result from impaired splenic function.

Surgical splenectomy
Congenital asplenia
In association with certain diseases or conditions (see “Differential Diagnosis”)

Besides splenectomy, when asplenia is known, patients with certain diseases are at risk of asplenia or hyposplenia (see “Differential Diagnosis”).
Asplenia or hyposplenia should be suspected in any patient with overwhelming infection with an encapsulated organism.

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