Cutaneous drug eruptions: a 5-year experience

The diversity of cutaneous drug eruptions encompasses many clinicopathologic entities.

Cases with a pathologic diagnosis of drug eruption from 2000 to 2005 were retrieved from our institution. The histologic slides were reviewed, the patterns of inflammatory changes were recorded, and a chart review was performed.

The majority of the cases (94%) were "morbilliform"-type rashes. Eighty-two percent of cases exhibited an inflammatory infiltrate confined to the superficial dermis. Eighty percent exhibited a perivascular and interstitial pattern of dermal infiltrate. The infiltrate was composed of lymphocytes and eosinophils in approximately 29% of cases, lymphocytes and neutrophils in approximately 10% of cases, and lymphocytes, eosinophils, and neutrophils in approximately 21% of cases. Eosinophils were present in only 50% of cases. Approximately half (53%) of the cases exhibited epidermal-dermal interface changes.

The cases were limited to those with a pathologic diagnosis of cutaneous drug reaction, thereby excluding any cases with drug-induced disease not specifically diagnosed (histologically) as such.

While the histologic features of most drug eruptions are not entirely specific, the finding of superficial infiltrates composed variably of lymphocytes, neutrophils, and eosinophils, either with or without interface changes, should suggest the possibility of a morbilliform drug eruption. Clinical correlation is very helpful to confirm the diagnosis. To our knowledge, this study is the most extensive documenting the histologic findings in morbilliform drug eruptions.