Elevated serum osteopontin levels in patients with severe cutaneous adverse drug reactions.

Osteopontin (OPN) was initially described as a protein involved in bone metabolism, but the roles played by OPN in the immune system and allergic reactions have attracted increasing attention. Here, we clarify the OPN-related dynamics of severe cutaneous adverse drug reactions, and assess whether the OPN level has utility for classifying such reactions and serving as a biomarker of severity. Serum OPN levels in patients with drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS), Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and erythema multiforme-type drug reaction (EM-DR) were quantified by ELISA. The OPN sources were analyzed by dual immunofluorescence assay of DIHS, SJS/TEN and EM-DR biopsy specimens. The serum OPN levels of DIHS/DRESS patients (489.1 ± 37.0 ng/mL) and SJS/TEN patients (508.5 ± 47.8 ng/mL) were significantly higher compared with controls (314.4 ± 14.3 ng/mL; p < 0.001). After treatment, the serum OPN level of DIHS/DRESS patients decreased to that of controls. In addition, OPN levels in DIHS/DRESS patients and SJS/TEN patients were higher than in patients with EM-DR (Mann-Whitney U test, p < 0.05). However, when the Kruskal-Wallis test was used to compare the OPN levels among the three groups of patients, the difference was not significant (p = 0.055). Dual immunofluorescence assay revealed that T lymphocytes and macrophages were the main OPN sources in DIHS, SJS/TEN and EM-DR patients. These data suggest that the OPN level can be used to evaluate the severity of inflammation in patients experiencing drug reactions.