1. Spleen and Thymus D S O’Briain, March 2009
150 g, receives 10% of cardiac output
Splenic artery branches surrounded by lymphoid tissue (white pulp); end in cords and sinuses of red pulp
Functions
Haemopoietic
Reservoir
Immunological
Filtration

2. Splenomegaly Infections Collagen disease Haemodynamic
Rheumatoid arthritis, Felty syndrome, SLE
Haemodynamic
Congestive failure, portal hypertension, portal vein thrombosis
Lympho- and myelo- proliferative diseases
Haemolytic anaemias
Miscellaneous
cysts, neoplasms, storage disease, amyloid

3. Hypersplenism Cytopenia Splenomegaly
isolated (red cell, white cell, platelet); combined; pancytopenia
Splenomegaly
Normal or increased marrow production
Reversal of cytopenia following splenectomy

4. Splenic atrophy or absence
Congenital
Traumatic (including surgery)
Vascular
sickle cell, embolus, thrombus
GI disease
Coeliac disease, inflammatory bowel disease
Miscellaneous
radiation, collagen disease, amyloid

5. Hyposplenism
Abnormal peripheral blood (Howell Jolly bodies, target cells, pitted red cells)
Immune defects
Encapsulated bacteria (Str pneumoniae, H influenza); may require vaccination, antibiotic cover

6. Splenic Lesions Rupture: immediate or delayed; splenosis
Fibrocongestive changes
Infarcts
Infections, granulomas
Immune thrombocytopenia
Leukaemia, CML, hairy cell leukaemia, myelosclerosis
Lymphomas
Cysts, tumours

7. Thymus Bilobed organ 50 g at puberty, 10 g in age
Epithelial cells and lymphocytes
Absent in some immune deficiency states
Enlargement: childhood, myasthenia gravis, autoimmune diseases
Tumours:
thymic carcinoid
germ cell tumours
lymphomas (Hodgkin, lymphoblastic lymphoma, large cell lymphoma)
thymoma

8. Thymoma Adults, mixture of epithelial cells and lymphocytes
Most (80%) encapsulated and histologically benign (benign thymoma)
Some (10%) similar histology but locally invasive (invasive thymoma; 75% 10-year survival)
Malignant thymoma (10%); histologically malignant, usually invasive, 25% 5-year survival
One-third of thymomas have myasthenia gravis;
hypogammaglobulinemia, erythroid hypoplasia may occur

9. Myastenia gravis Myopathy with antibodies to
acetylcholine receptor molecule (and a similar thymic epitope)
skeletal muscle cells (cells which also occur in the thymus)
Other autoimmune disease in 10%
Most (65%) have lymphoid follicular hyperplasia (these respond best to thymectomy)
Thymoma in 10% and normal thymus in 25%