Genes, Infections and Drug Allergies
I read an exciting article in USA Today (October 25th) about Genes and Medicine. The article, “Genes are Part of the Puzzle”, shows how medical research is moving to personalized medicine based on your genetic fingerprint (genome). The article is careful to state that while you can have your entire genetic make-up analyzed, even expert doctors don’t know what to do with much of the data. The one practical area for genetic testing in the field of allergies is drug allergies in particular.
Allergy specialists have known for a long time that there were patients who complained that they developed allergic reactions to many different medications-especially antibiotics. As allergists, until recently, we had limited allergy testing to evaluate these patients. Penicillin allergy skin testing has been around for decades and is a valuable test to see if a person is allergic to penicillin, and more importantly has a 99% negative predictive value that you won’t have a reaction to it if your skin test is negative.
The most clinically useful markers right now for prevention of an allergic reaction to a drug are the following:
- Patients with HIV/AIDS who require Abacavir should be pre-tested if possible for the HLA-B5701 marker. 4% of patients with this marker can develop a fever, rash, gastrointestinal and respiratory illnesses. HIV patients are also at a much higher likelihood (44-70%) to have an allergic skin reaction to Sulfonamide medication.
- Diabetic patients that require Insulin need to be aware that Insulin allergy can develop in those patients with HLA-DR3 marker.
- Infectious Mononucleosis is classically associated with a generalized rash if the patient is given Amoxicillin; this can occur when initially the physician sees the severe sore throat and treats it as a Strep infection. This type of reaction with Amoxicillin can also occur with a patient with Chronic Lymphocytic Leukemia.
On a different note, there has been no recent scientific evidence that shows a seafood allergy makes a person more likely to get a Radiocontrast dye reaction; the best thing for a patient with a prior reaction to a diagnostic test with dye is to be pre-treated with oral cortisone and antihistamines in advance of the test.
The exciting research from Harvard’s affiliated medical school, Dr. Maryanne Castells has shown patients allergic to chemotherapy medications can be successfully desensitized and receive the appropriate treatment for their cancers.
Dr. Dean Mitchell
Mitchell Medical Group, NYC & Long Island