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The Case of Baby Joe

Chronic Infections in an Infant


Kristen L.W. Walton
Department of Biology
Missouri Western State University


This interrupted case study follows the declining health of an infant who suffers from recurrent infections and finally is diagnosed with severe combined immunodeficiency (SCID). The case was developed for use in an undergraduate upper-level immunology course to supplement discussion of B and T cell development and the generation of antibody diversity. It could also be modified for use in a genetics class, with emphasis on the molecular aspects of RAG-mediated recombination and inheritance patterns of the disease, or a pathophysiology class, with emphasis on the physiology underlying the symptoms.


  • Assess the likelihood of genetic versus environmental causes of a medical condition in an infant.
  • Analyze a data set and use the analysis to predict the most likely stage(s) of immune cell development that are disrupted.
  • Determine how alterations in various immune cells could explain observed symptoms.
  • Explain the role of RAG enzymes in B cell and T cell development.
  • Predict possible treatment options for immunodeficiency caused by genetic mutations in RAG enzymes.


Immunology; immune system; antibody diversity; B cell; T cell; T cell receptor; TCR; recombination activating gene enzyme; RAG; immunodeficiency; somatic recombination recessive allele; severe combined immunodeficiency; SCID; infection

Topical Areas


Educational Level

Undergraduate lower division, Undergraduate upper division



Type / Methods




Subject Headings

Biology (General)  |   Medicine (General)  |   Genetics / Heredity  |  

Date Posted


Teaching Notes

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Kathy Zanin, Assistant Professor
Department of Biology
The Citadel
Charleston, SC
The students enjoyed this case. I think it was well done, and it is a fun way to learn.

I made only minimal modifications:

  1. I asked my students to read relevant passages from their textbook (Kuby’s Immunology) rather than consulting the online resources.
  2. I used the info you provided online to create a PowerPoint presentation, and I added a few images that I got from a Google image search for a normal baby boy, a child getting an ear exam, a photo of David Vettle, etc.
  3. I have a small class, so we worked on the case as a whole, and the class split into smaller groups just to read and study the possible causes of SCID.
My students posed an excellent question about the bone marrow transplant treatment: If the patient has SCID, why does the bone marrow donor have to be a tissue match? How can a person with SCID reject foreign transplants?