SCID (Severe Combined Immunodeficiency Disease)
  • Heterogenous disorder
  • Autosomal recessive and X-linked recessive forms
  • Both T-cell and B-cell immunity impaired (generally greater loss of T-cell immunity)
  • Abnormal differentiation of stem cells caused by either intrinsic defect or abnormal thymic signals for differentiation
  • Usually succumb to opportunistic infections in 1st year of life
    • Pseudomonas
    • Candida
    • Pneumocystis
    • Cytomegalovirus (CMV)
    • Hepres simplex virus (HSV)
  • 50% of patients with the autosomal recessive form lack adenosine deaminase, accumulating deoxy-ATP, which is toxic to lymphocytes
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