Cross Reactivity of Acute Generalized Exanthematous Pustulosis Among Proton Pump Inhibitors: Case Report

Acute generalized exanthematous pustulosis (AGEP) is an acute pustular eruption characterized by widespread nonfollicular sterile pustules. AGEP is a rare adverse drug reaction with an incidence of 1 to 5 cases per million per year. This condition was accidentally discovered in a patient treated with two different proton pump inhibitors (PPIs) consecutively.

A 47-year-old male developed pustulosis within a couple of hours after being injected with pantoprazole 40 mg. After 3 days of stopping pantoprazole, the patient was injected with lansoprazole 30 mg, and pustulosis redeveloped.

Several studies have reported that pantoprazole can induce AGEP in sensitive patients, but the incidence is rare. In the current case, two different PPI drugs induced the condition in the same patient. This showed cross-reactivity between pantoprazole and lansoprazole in inducing AGEP. The current study is the first case report on cross-reactivity of PPIs in AGEP.

According to previous results, cross-reactivity in PPIs is largely due to a similar chemical structure. Omeprazole, esomeprazole, and pantoprazole have changed their benzimidazole rings, while lansoprazole and rabeprazole have modified their pyridine rings. Therefore, cross-reactivity is often observed within the same group of benzimidazoles or pyridines. In the current case, the cross-reactivity cannot be explained by those patterns. A safe alternative PPI can be identified by a skin test, which has high specificity for immediate hypersensitivity reactions to PPIs.

Based on the results, pantoprazole and lansoprazole led to the consecutive induction of AGEP. Cross-reactivity between both drugs cannot be explained by the general patterns in PPIs. Therefore, individuals who show hypersensitivity to pantoprazole must undergo a skin test before receiving another PPI.