Download Spleen-thymus-09

Spleen and Thymus
D S O’Briain, March 2009
Spleen
• 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
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Haemopoietic
Reservoir
Immunological
Filtration
Splenomegaly
• Infections
• Collagen disease
• 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
Hypersplenism
• Cytopenia
• isolated (red cell, white cell, platelet); combined;
pancytopenia
• Splenomegaly
• Normal or increased marrow production
• Reversal of cytopenia following
splenectomy
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
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
Splenic Lesions
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Rupture: immediate or delayed; splenosis
Fibrocongestive changes
Infarcts
Infections, granulomas
Immune thrombocytopenia
Leukaemia, CML, hairy cell leukaemia, myelosclerosis
Lymphomas
Cysts, tumours
Thymus
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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
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
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%