AGEP y pruebas de parche...

 Published in Dermatology

Journal Scan / Review · March 15, 2022

Results of Patch Testing in AGEP

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• This literature review characterized the relationship between acute generalized exanthematous pustulosis (AGEP) and results of patch testing to culprit medications. A total of 93 drugs causing AGEP were identified, which resulted in 259 positive patch test reactions. Beta-lactam antibiotics, other antibiotics, and iodinated contrast media were among the many agents that cumulatively accounted for almost 60% of all reactions. The sensitivity, techniques, and safety of patch testing in AGEP were also discussed.

• This review suggests that, although mild recurrence may be noticed occasionally, patch testing is mostly safe and can be regarded as the first-line diagnostic test to be performed to determine the causative drug in patients with AGEP.

–  Joshua R. Ortego, MD

Written by Stephen E. Helms MD, FAAD

One of the most difficult decisions we may have to make is "which drug may or may not" be causing this eruption. I too often am faced with eczematous rashes that on biopsy are reported as a dermatitis but have a comment listing drug induced mentioned as a consideration. That is bad enough but when we see patients with a severe cutaneous adverse reaction (SCAR) to a drug, such as acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), or toxic epidermal necrolysis (TEN), we are tasked with trying to define the culprit drug. Unfortunately, we have not perfected any lab test or skin test that can tell us the answer 100% of the time. One thing we as dermatologists can do though that may help is applying patch tests to at least a few medications that are commercially available through Chemotechnique Diagnostics or Smart Practice Dermatology/Allergy. After reviewing the literature, we may prepare medications in petrolatum, water, or alcohol also, but these are not standardized. A very limited number of dermatologists may also attempt to identify the causative agent using Intradermal skin testing or the Lymphocyte Tranformation Test (LTT). As Dr. de Groot points out in his excellent review using AGEP as an example, it is clear that overall from this and other articles that we face about a 50% accuracy rate. He notes that 93 drugs were identified that have together caused 259 positive patch tests in 248 patients suffering from AGEP. Patch testing has been shown in other articles to be helpful to assess drug imputability in AGEP with positive tests reported with more than 20 different drugs (1,2), and even though testing is not close to delivering 100% reliability, it is usually quite safe and has been accurate to different degrees with regard to different reactions and with different medications (3,4). This is better than nothing, but we must also realize a very important caveat and that is that false negatives may be misleading. This is not serious with eczematous reactions if the patient is rechallenged with the suspect drug that has falsely been labeled as "not the one."

This article by Dr. de Groot, who tirelessly and continually teaches us so much dermatology, not only helps us understand what is known about testing for AGEP and other SCARs but also provides informative tables and an amazing list of references for those who wish to study testing for drug allergy. This demonstrates that more needs to be done to help us with such a dilemma.

References

1. Serra D, Gonçalo M, Mariano A, et al. Pustular psoriasis and drug-induced pustulosis. G Ital Dermatol Venereol. 2011;146:155–158. https://www.minervamedica.it/en/journals/Ital-J-Dermatol-Venereol/article.php?cod=R23Y2011N02A0155
2. LaBerge L, Pratt M. MD Immediate and Delayed Hypersensitivity to Systemic Corticosteroids: 2 Case Reports. Dermatitis. 2012;23(6):288–290. 10.1097/DER.0b013e318277ca22
3. Aquino MR, Sher J, Fonacier L. Patch testing for drugs. Dermatitis. 2013;24:205–214. https://doi.org/10.1097/der.0b013e3182a0d38a
4. Barbaud A, Collet E, Milpied B, et al. A multicentre study to determine the value and safety of drug patch tests for the three main classes of severe cutaneous adverse drug reactions. Br J Dermatol. 2013;168:555–562. https://doi.org/10.1111/bjd.12125

Abstract

The literature on positive patch test results in acute generalized exanthematous pustulosis (AGEP) is reviewed. 93 drugs were identified that have together caused 259 positive patch tests in 248 patients suffering from AGEP. The drug classes causing the highest number of reactions are beta-lactam antibiotics (25.9%), other antibiotics (20.8%), iodinated contrast media (7.3%) and corticosteroids (5.4%), together accounting for nearly 60% of all reactions. The highest number of reactions to individual drugs was to amoxicillin (n=36), followed by pristinamycin (n=25), diltiazem (n=14), amoxicillin-clavulanic acid (n=13), clindamycin (n=11) and iomeprol (n=8); 59 of the 93 drugs each caused a single case only. The "Top-10" drugs together caused over 50% of all reactions. The sensitivity of patch testing (percentage of positive reactions) in patients with AGEP is largely unknown, but may generally be around 50%, which also applies to pristinamycin. Patch testing in AGEP appears to be safe, although mild recurrence of AGEP skin symptoms or other rashes may occur occasionally. Clinical aspects of AGEP, including epidemiology, etiology and pathophysiology, clinical features, histology, treatment, and prognosis are briefly presented, as are diagnosing the disease and identifying the culprit drugs with patch tests, intradermal tests, in vitro tests, and challenge tests. This article is protected by copyright. All rights reserved.

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Results of patch testing in Acute generalized exanthematous pustulosis (AGEP): a literature review

Contact Derm 2022 Feb 20;[EPub Ahead of Print], AC de Groot