User:PriceDL/Notes/Primary immune deficiencies


 * Immune deficiency is a state in which immune system's ability to fight infections and cancers is reduced or absent.
 * Primary immune deficiency is when the cause originates in the immune system itself

T-cell Deficiencies
Increases susceptibility to viral, fungal and some bacterial infections, and early malignancy

Bare lymphocyte syndrome
Also called class I/II MHC deficiency
 * Defect of regulatory factor X or class II transactivator
 * Absent expression of HLA molecules within thymus -> lymphocytes fail to develop
 * Type 1: MHC I absent (low CD8 cells)
 * Type 2: MHC II absent (low CD4 cells)
 * Type 2 is most common (100 patients worldwide)
 * Less IgA and IgG made because B-cell class switch requires CD4
 * Associated with sclerosing cholangitis
 * Unwell by 3 months of age

DiGeorge's Syndrome
Remember with CATCH-22 (cardiac abnormality, abnormal facies, thymic aplasia, cleft palate, hypocalcemia/hypoparathyroidism)

DiGeorge Syndrome is caused by the deletion of a small segment of chromosome 22. It results in the defective development of the 3rd and 4th pharyngeal pouches, which form the oesophagus, thymus and heart. They have very low levels of T cells due to the absent thymus. May be treated by a thymus transplant.

Associated with defective development of pharyngeal pouch system (3rd and 4th, oseophagus, thymus, heart)
 * Usually heterozygous chromosomal deletion of 22q11.2.
 * 75% sporadic
 * Low set ears, cleft lip and palate
 * Low calcium
 * Susceptibility to viral infection
 * Very low numbers of mature T cells (absent thymus)
 * Treated by thymus transplant

Treatment of T-cell deficiencies

 * Infection prophylaxis
 * IgG replacement if necessary
 * Other treatments