Abstract

BACKGROUND Allergic contact dermatitis (ACD) is histologically challenging to differentiate from other forms of spongiotic/eczematous dermatitis. Previous studies have variably supported the specificity of dermal eosinophils, eosinophilic spongiosis, and Langerhans cell collections (LCCs) in ACD. METHODS With IRB approval, selected histologic parameters of patients who underwent biopsy and patch testing were blindly reviewed by an experienced board-certified dermatopathologist and at least one other dermatologist and/or pathologist. Statistical analyses included Fisher exact test and logistic regression with Stata®. RESULTS 164 cases (105 positive for ACD, 59 negative) fulfilled inclusion criteria. Forty-seven cases had epidermal spongiotic vesicles with Langerhans cells. LCCs were more likely to be found in ACD cases (34/47, 72%) than non-ACD cases (13/47, 28%) (p = 0.033). Using multivariable logistic regression, LCCs had an odds ratio (OR) of 3.23 (95% confidence interval, CI, 1.04-10.0), p = 0.04, in association with ACD diagnosis. Eighteen cases had a heavy dermal eosinophilic infiltration (greater than 100 dermal eosinophils in five 40x fields). Non-ACD cases (11/18, 61%) were more likely than ACD (7/18, 39%) to have heavy dermal eosinophilic infiltration (p = 0.034); OR for ACD was 0.32 (95% CI 0.11-0.91), p = 0.03. No statistically significant differences were found for eosinophilic spongiosis, papillary dermal edema and hypogranulosis, follicular spongiosis, and dermal multinucleated dendritic cells. CONCLUSION To our knowledge, this study is the largest to date confirming that ACD is associated with LCCs. A novel, unexpected finding is the association of heavy dermal eosinophilic infiltration with a non-ACD diagnosis.