Confusion in determination of two types of cutaneous adverse reactions to drugs, maculopapular eruption and erythema multiforme, among the experts: A proposal of standardized terminology

The clinical classification of cutaneous adverse reactions by drugs should be clearly distinguished to avoid conceptual confusion and inconsistency. Although dermatologists appear to have established a roughly common consensus for cutaneous adverse reactions, some types are more rigorously defined than other, possibly misleading classifications. To assess the consensus on the clinical classifications, we investigated the concordance rate of diagnosis by Japanese experts through a snap visual inspection of various clinical pictures exhibiting erythema multiforme and maculopapular eruption types of cutaneous adverse reactions. The experts were shown images on a screen and were then asked to decide whether to classify cases as maculopapular eruption or erythema multiforme type, and the concordance rates were calculated. Overall, the mean concordance rate was 71.6% (standard deviation, 17.3%), and only 33.8% of cases had a 90% or more concordance rate. Our study shows that the determinations of erythema multiforme and maculopapular eruption types by the existing classification criteria were confusing even among experts, which prompted us to standardize the terminology. We propose clinically defining erythema multiforme type as generalized macules mainly of 1 cm or more with a tendency of elevation and coalescence, and maculopapular eruption type as generalized erythema other than erythema multiforme type. Currently, the clinical definitions of cutaneous adverse reactions are poorly described, which may be problematic upon analyzing large volumes of data. Our proposal for a new terminology will enhance the accuracy and consistency of information for the correct analysis of cutaneous adverse reactions.