Reply to the case discussion of colleagues

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Case Discussion 1

In this scenario, an otherwise healthy 16-year-old boy is diagnosed with strep pharyngitis (strep throat) via an in-office rapid strep test, which tests for group A streptococcus bacteria (Cohen et al., 2016). He has prescribed penicillin, which is the antibiotic of choice for a patient with no known allergy to penicillin given that there is no strain of group A streptococcus bacteria that is resistant to it (Centers for Disease Control, 2022).

Unfortunately for this young man, upon taking his first dose of penicillin he experienced an anaphylactic response, as evidenced by lip and oral swelling and breathing difficulties. This response is the most rapid and severe, and characteristic of a Type I hypersensitivity reaction, or IgE-mediated response resulting from the sensitization of mast cells by the binding of IgE to Fc protein receptors on the plasma membranes (McCance & Huether, 2019).

Once sensitized, further exposure results in degranulation and release of histamine causing bronchial constriction and increased vascular permeability producing the breathing difficulties and lip and oral swelling respectively seen in this patient (Patterson & Stankewicz, 2020; McCance & Huether, 2019).

Though type IV (IgG-mediated) hypersensitivity reactions are found in penicillin allergies, the primary result of this would be related to a delayed hypersensitivity mechanism resulting in dermatologic symptoms, not reported in this case (McCance & Huether, 2019).

Of note, Type I allergic responses can only occur with prior sensitization of the Fc proteins on mast cells. This patient was presented as having no known drug allergies, and while he could have taken penicillin in the past, which could have resulted in sensitization without evidence of allergic reaction, consideration should be given to the possibility that the patient carries a genetic erroneous beta (b)-lactam allergy.

This could result in the allergic reaction without previously having taken the drug (Bhattacharya, 2010). Knowing the patient has a serious sensitivity to penicillins, the clinician should be aware of a cross-sensitivity to cephalosporins due to similarities in the chemical structure (Patterson & Stankewicz, 2020).

Though research has shown females have a greater predisposition to penicillin allergy than males, the case presentation demonstrates a clear hypersensitivity reaction in this patient (Park et al., 2007).


Bhattacharya, S. (2010). The Facts About Penicillin Allergy: A Review. Journal of Advanced Pharmaceutical Technology and Research, 1(1), 11–17.

Centers for Disease Control and Prevention. (2022, June 27). Pharyngitis (strep throat): Information for clinicians. Centers for Disease Control and Prevention.,that%20is%20resistant%20to%20penicillin.

Cohen, J. F., Bertille, N., Cohen, R., & Chalumeau, M. (2016). Rapid antigen detection test for group A streptococcus in children with pharyngitis. Cochrane Database of Systematic Reviews.

McCance, K., & Huether, S. (2019). Pathophysiology: The biologic basis for disease in adults and children (8th ed.). Elsevier.

Park, M. A., Matesic, D., Markus, P. J., & Li, J. T.-C. . (2007). Female sex as a risk factor for penicillin allergy. Annals of Allergy, Asthma & Immunology, 99(1), 54–58.

Patterson, R. A., & Stankewicz, H. A. (2020). Penicillin Allergy. PubMed; StatPearls Publishing.

Reply to the case discussion of colleagues


Hello Suzanne,

Great explanation of the type I hypersensitivity presented in this week’s case study. I was interested to learn about the genetic component and the possibility of the beta (b)-lactam allergy you spoke of and did not consider it when I was reviewing this patient.

My assumption was that the patient likely took penicillin before making him hypersensitive to it now. Upon further research, I found an article that studied the prediction of penicillin allergy through genome mapping.

This study researched 387 patients with immediate allergic reactions to B-lactams and found significant associations between gene variants HLA-DRA and an allergy to penicillin (Gueant, et al., 2015). It is important to note that this study confirmed predictors of penicillin allergies but not to cephalosporins.

Although rare, it is interesting to understand that there could be a genetic component to those with allergies to penicillin. Another aspect to consider with this case study is how recurring strep throat could be a genetic component.

Germinal centers of individuals with recurrent strep were found to be smaller, there were fewer B and helper T cells and two variants in the HLA genomic region could make them more susceptible to tonsillitis (Crotty & Dan, 2019).



Crotty, S., & Dan, J. (2019). Recurrent group A streptococcus tonsillitis is an immunosusceptibility disease involving antibody deficiency and aberrant TFH cells. Science Translational Medicine, 11(478). doi:DOI: 10.1126/scitranslmed.aau3776

Gueant, J.-L., Romano, A., Cornejo-Garci, J.-A., Oussalah, A., Chery, C., Blanca-Lopez, N., . . . Gaeta, F. (2015). HLA-DRA variants predict penicillin allergy in genome-wide fine-mapping genotyping. Journal of Allergy and Clinical Immunology, 135(1), 253-259. doi:

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