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The spleen and its disorders 

The spleen and its disorders

Chapter:
The spleen and its disorders
Author(s):

D. Swirsky

DOI:
10.1093/med/9780199204854.003.220404
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date: 30 March 2017

The spleen is the single largest lymphoid organ in the body, performing important immune functions. Intrinsic disorders of the spleen are very rare: its importance in clinical practice relate to the causes of its enlargement, its hyperfunction (hypersplenism), acute rupture, and the consequences of its physical or physiological absence.

Splenomegaly

Causes can broadly be divided into (1) infective—acute and chronic, with the prevalence of particular disorders being very dependent on geography; globally, most cases of splenomegaly are caused by parasitic infections, particularly malaria, leishmaniasis, and schistosomiasis; (2) congestive—most commonly portal hypertension; (3) haemolytic anaemias—both hereditary (including structural haemoglobinopathies and some thalassaemias) and acquired; (4) primary blood disorders—causes of massive splenomegaly include chronic myeloid leukaemia, chronic lymphocytic leukaemia, hairy cell leukaemia, and myelofibrosis; (5) malignant lymphomas; (6) connective tissue disorders—e.g. systemic lupus erythematosus (SLE), Felty’s syndrome; (7) others—including storage diseases, e.g. type I Gaucher’s disease.

Hypersplenism

Any cause of splenomegaly may give rise to hypersplenism, manifest as (1) variable peripheral blood cytopenias; (2) a cellular or hypercellular bone marrow; (3) premature release of cells into the peripheral blood, resulting in a mild reticulocytosis with nucleated red cells and occasional immature granulocytes. Other features include decreased red cell and platelet survival, and hypervolaemia.

Deficient splenic function

The most serious consequence of splenectomy or hyposplenism/asplenia is vulnerability to overwhelming infection, which carries a very high mortality rate and is most frequently caused by Streptococcus pneumoniae.

All patients without a functioning spleen require vaccination against S. pneumoniae, haemophilus, and Neisseria meningitides, with additional lifelong antibiotic prophylaxis in some situations. Special warnings, advice about avoidance, and prophylaxis are required for those in or travelling to areas endemic for malaria and babesiosis.

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