Severe Combined Immunodeficiency (SCID) - Immunology USMLE Step 1

Severe Combined Immunodeficiency (SCID) - Immunology USMLE Step 1
* Both B and T cell disorder.
* defective IL-2R gamma chain (most common X-linked recessive).
* adenosine deaminase deficiency (autosomal recessive).
* RAG mutation  VDJ recombination defect
* Failure to thrive, chronic diarrhea, thrush
* Recurrent viral, bacterial, fungal, and protozoal infections
* Decreased T-cell receptor excision circles (TRECs)
* Part of newborn screening for SCID
* Absence of thymic shadow (CXR)
* Germinal centers (lymph node biopsy), and  cells (flow cytometry)