Immunodeficiencies: T-cell and B-cell disorders: Pathology review

00:00 / 00:00



Immunodeficiencies: T-cell and B-cell disorders: Pathology review



Immunodeficiencies: T-cell and B-cell disorders: Pathology review

USMLE® Step 1 questions

0 / 7 complete


USMLE® Step 1 style questions USMLE

of complete

A 20-year-old woman presents to her primary care physician’s office for evaluation of a rash under her breasts. She first noticed the rash two days ago while bathing. The patient reports recurrent rashes of similar appearance affecting her face and limbs since the age of two. She was recently treated for oral thrush at a local clinic. Past medical history is significant for hypothyroidism managed with levothyroxine. Family history is significant for a brother who experienced similar cutaneous symptoms and died of fulminant hepatitis at the age of six. She does not use tobacco, alcohol, or illicit drugs. Vitals are within normal limits. Physical examination demonstrates red-brown, beefy, homogenous patches under the breasts and massive erythematous-desquamating dermatosis involving the face, limbs and nails. Genital examination shows multiple labial fissures. Intraepidermal injection of Candida antigens yields no reactogenicity. Which of the following is the most likely diagnosis?


Gaia, a 6 year old girl, is brought to the clinic by her parents because she’s been having diarrhea and abdominal cramps for the past few weeks.

When you ask about her clinical history, her parents tell you that Gaia was diagnosed with celiac disease a few years back; however, they point out that she's stopped consuming any food products that may contain gluten altogether.

You decide to first run stool tests, which reveal the presence of the parasite giardia lamblia.

In addition, Gaia’s parents tell you that she has a history of asthma and allergic rhinitis, so you also order an immunoglobulin test, which shows low IgA and increased IgE levels in her blood.

Next comes Joe, a 10 year old boy that’s brought to the clinic because he fell and broke his arm.

Upon physical examination, you notice a red, weeping rash on his scalp.

You also notice that there’s a skin abscess on his leg that lacks any surrounding warmth and redness.

Joe’s parents tell you that he develops abscesses like that all the time.

You order an immunoglobulin test for Joe too, which reveals increased IgE but normal IgA levels.

Based on the initial presentation, both cases seem to have some form of immunodeficiency, meaning that their immune system's ability to fight pathogens is compromised.

Immunodeficiencies can be classified according to the cell of the immune system that is defective, into B cell and T cell disorders, which respectively lead to a deficiency in humoral or antibody-mediated and cell-mediated immune responses.

Let’s begin with B cell disorders, starting with Bruton or X-linked agammaglobulinemia, or XLA for short.

This is caused by a mutation in the BTK gene, which is found on the X chromosome.

XLA is an X-linked recessive condition, so it almost exclusively manifests in biological males because they have only one X chromosome.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Analysis of Clinical Presentations of Bruton Disease: A Review of 20 Years of Accumulated Data from Pediatric Patients at Severance Hospital" Yonsei Medical Journal (2008)
  4. "Allergy and Asthma: Practical Diagnosis and Management" McGraw Hill Professional (2007)
  5. "Selective IgA deficiency (SIgAD) and common variable immunodeficiency (CVID)" Clinical and Experimental Immunology (2000)
  6. "Long-term follow-up of health in blood donors with primary selective IgA deficiency" Journal of Clinical Immunology (1996)

Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.