Pathophysiology
1) group of disorders characterized by severe immunodeficiency secondary to deficiency in both cell-mediated and humoral immune functions 2) infections are associated with organisms that are not normally pathogenic thus these patients can not be immunized with live-attenuated vaccines
Signs and Symptoms
1) chronic meningitis 2) encephalitis 3) dermatomyositis (rash, edema, and myositis) 4) hepatitis 5) Guillain-Barre syndrome
Associated Conditions
blood transfusions often cause fatal graft versus host disease
Biochemistry
1) some forms are marked by mutations of receptors for T cell growth 2) defective B and T cells 3) defective IL-2 receptors 4) aborted thymocyte differentiation
Inheritance/Epidemiology
both X-linked (IL-2RG deficient types) and autosomal recessive (JAK-3 deficient types)
Treatment
1) removal from nonhygienic environments 2) long-term antibiotics 3) gene therapy has shown promising initial results, but has been plagued by leukemia-like side effect of the adenovirus vector
Tips for USMLE
Known gene deficiencies – 1) recombinase-activating gene (RAG-1 and RAG-2) deficiency of 11p13 2) ADA deficiency on 20q13.11 3) interleukin 2 receptor gamma chain (IL-2Rgamma) deficiency on Xq13 4) Janus-associated kinase 3 (JAK3) deficiency on chromosome 19p13.1 5) DNA-dependent protein kinase (PK) deficiency on 8q11
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