Background: Acantholysis is the histologic hallmark in the diagnosis of all forms of pemphigus. However, biopsy specimens of early lesions may lack acantholysis and show only eosinophils in the epidermis in areas of spongiosis (eosinophilic spongiosis). We report two cases of pemphigus foliaceus and two cases of unclassified pemphigus (foliaceus vs vulgaris) in which neutrophilic spongiosis was the prominent histologic finding.
Observations: Four patients developed blistering skin disorders that spared the mucous membranes. Skin biopsy specimens in all four patients showed striking infiltration of neutrophils into the epidermis. Acantholysis was focal and was absent in some sections. Direct immunofluorescence demonstrated intercellular deposition of IgG and C3 within the epidermis in all cases. There was no IgA deposition. Gram's stains were negative for bacteria in three cases and revealed Gram-positive cocci overlying an eroded area in one case. However, the neutrophilic spongiosis in this case extended well beyond the area of impetiginization.
Conclusions: The histologic differential diagnosis of neutrophils in the epidermis includes pustular psoriasis, subcorneal pustular dermatosis, intraepidermal neutrophilic IgA dermatosis, superficial IgA pemphigus, toxic shock syndrome, Sweet's syndrome, and superficial fungal and bacterial infections. We conclude that pemphigus be added to this differential diagnosis and recommend direct immunofluorescence when neutrophilic spongiosis is observed.