A pilot study evaluating biomarker development for drug-induced chronic eczematous eruptions of aging individuals

The Frequency and Utility of Drug Cessation Trials in Older Adults With Chronic Eczematous Dermatitis of Unknown Etiology: A Retrospective Cohort Study

Background: Eczematous dermatitis is a major cause of recalcitrant pruritic eruptions in older adults. Although some medications have been implicated, there are limited data demonstrating the utility of medication changes. Objective: To investigate the utility and possible harms of drug cessation trials (DCTs) in chronic eczematous eruptions in the aging (CEEA). Methods: This is a retrospective cohort study utilizing electronic health records of DCTs in adults older than 65 years with CEEA. Results: We identified 646 patients >65 years with new onset eczematous eruptions, 89 (14%) of whom had no identifiable etiology. In this cohort, 35 patients underwent a total of 40 DCTs. Although there was mention of improvement in 17.5% (7/40), all patients sought tertiary care for their persistent rash. Negative outcomes occurred in 45% (18/40), all of which were due to exacerbation of a comorbidity that the medication was prescribed to treat. Conclusion: Our experience suggests that patients with CEEA undergo DCTs that do not improve their dermatitis and can lead to dangerous worsening of underlying conditions. Further study of the etiology of CEEA is needed.

The Role of Patch Testing in Evaluating Delayed Hypersensitivity Reactions to Medications

Confirming drug imputability is an important step in the management of cutaneous adverse drug reactions (CADR). Re-challenge is inconvenient and in many cases life threatening. We review the literature on ideal patch testing technique for specific CADRs. Testing should be performed approximately 3 months after the resolution of the eruption using standard patch testing techniques. Commercially available patch test preparations are available for a minority of drugs, so in most cases, testing should be performed with the drug at various recommended concentrations and in different vehicles. Testing to all known excipients, such as dyes, vehicles and preservatives is also important. Immunosuppressive medications should be discontinued or down titrated to the lowest tolerable dose to decrease the risk of false negative reactions. We provide an overview of expert recommendations and extant evidence on the utility of patch testing for identifying the culprit drug in common CADRs and for specific drug or drug classes. Overall, there appears to be significant variability in the patch test positivity of different drugs, which is likely the result of factors intrinsic to the drug such as dermal absorption (as a function of lipophilicity and molecular size) and whether the drug itself or a downstream metabolite is implicated in the immune reaction. Drugs with high patch test positivity rates include beta-lactam antibiotics, aromatic anticonvulsants, phenytoin, and corticosteroids, among others. Patch testing positivity varies both as a function of the drug and type of CADR. The sum of the evidence suggests that patch testing in the setting of morbilliform eruptions, fixed drug eruption, acute generalized exanthematous pustulosis, and possibly also drug-induced hypersensitivity syndrome, photoallergic and eczematous reactions may be worthwhile, although utility of testing may vary on the specific drug in question for the eruption. It appears to be of limited utility and is not recommended in the setting of other complex CADR, such as SJS/TEN and leukocytoclastic vasculitis.

Eczematous Drug Eruptions

Eczematous drug eruptions are a heterogenous group of skin reactions that resemble eczema both clinically and histologically. We reviewed the literature and cataloged the systemically administered medications that cause these eruptions, along with their characteristic clinical presentations. We identified three primary pathophysiologic etiologies: (1) cutaneous immunomodulation, (2) skin dehydration, and (3) delayed hypersensitivity. Notably, eczematous eruptions caused by altered immunity in the skin may be increasing in incidence as some responsible drugs, in particular biologic therapies (such as tumor necrosis factor-α and interleukin-17 inhibitors) and targeted cancer treatments (including immune checkpoint inhibitors and epidermal growth factor receptor inhibitors), become more commonly employed in clinical practice. Other notable causes of eczematous eruptions include antiviral agents for hepatitis C virus and cardiovascular medications in elderly individuals, and notable subtypes of eczematous reactions include systemic contact dermatitis and photoallergic reactions, which are also discussed. The diagnostic gold standard is drug rechallenge and most reactions may be treated effectively with emollients, topical corticosteroids, and oral antihistamines.