A delayed hypersensitivity reaction to enfuvirtide after rechallenge

Enfuvirtide is beneficial in patients with limited treatment options. We report this case to highlight the possibility of a delayed hypersensitivity reaction as an important potential side-effect of enfuvirtide treatment. A highly antiretroviral treatment-experienced man was commenced on a new regimen containing enfuvirtide. Prophylaxis for Pneumocystis jirovecii pneumonia was started using trimethoprim/sulphamethoxazole (TMP-STX) simultaneously. Ten days later, he developed a maculopapular rash on the chest and abdomen without any systemic features. Both enfuvirtide and TMP-STX were discontinued. Re-introduction of enfuvirtide occurred in a hospital setting. Before re-challenge, haemodynamic observations were stable. The rash re-appeared involving the whole body 5 hours post-dose and was associated with fever (temperature 38.4), nausea and a presyncopal episode. Hypersensitivity to this drug occurred immediately post-dose in phase III trials. Enfuvirtide is a useful drug in those with reduced drug options. The possibility of delayed hypersensitivity has not been reported previously.