Tissue eosinophilia not linked as differentiating feature of subacute cutaneous lupus erythematosus

The eosinophil ratio in patients with drug-induced subacute cutaneous lupus erythematosus was not different from the ratio in patients with nondrug-induced subacute cutaneous lupus erythematosus, according to study results.

Researchers from a university-affiliated dermatology and dermatopathology practice examined medical records retrospectively to determine whether tissue eosinophilia is a differentiating histopathologic feature of drug-induced subacute cutaneous lupus erythematosus. They compared patients with drug-induced and nondrug-induced subacute cutaneous lupus erythematosus.

The final analysis included 15 patients in the drug-induced group, and 44 patients in the nondrug-induced group, for a total patient population of 59.

A dermatopathologist masked to the etiologic associations reviewed corresponding histopathologic specimens and calculated an eosinophil ratio for each patient. The ratio was calculated as the mean eosinophil score (averaging eosinophil counts from 10 high-power histologic fields) divided by the intensity of inflammation.

The researchers compared ratios for both groups using the Mann-Whitney test.

The mean eosinophil ratio in the drug-induced group was 0.11 vs. 0.004 in the nondrug-induced group, which the researchers said was not a significant difference (P=.34).

Both groups demonstrated mucin disposition, but no significant differences were observed between the two groups (P=.18).

Superficial and deep inflammatory infiltrate occurred in 67% of patients (n=10) in the drug-induced group and 55% of patients (n=24) in the nondrug-induced group. The rate of periadnexal inflammation was 80% (n=12) in the drug-induced group and 84% (n=37) in the nondrug-induced group. All 15 patients in the drug-induced group demonstrated basal layer liquefaction with dyskeratosis vs. 84% of patients (n=37) in the nondrug-induced group.

“Tissue eosinophilia is not a differentiating histopathologic feature of [drug-induced subacute cutaneous lupus erythematosus],” the researchers wrote. “Careful review of a patient’s drug history in correlation with clinical findings remains the standard for identifying a drug as an etiologic or exacerbating factor in patients with [subacute cutaneous lupus erythematosus].”