[Six cases of spring DRESS].

Background: An association between herpes virus reactivations and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) is accepted. We report six cases of DRESS with viral reactivation occurring within a single 1-month period. We attempted to find a common factor for these six cases and carried out clinical and virological examinations. Before and after this "epidemic", the mean number of cases of DRESS seen at the same centre was one per quarter, making the occurrence of six cases within a single month all the more remarkable and prompting us to seek an explanation.

Patients And Methods: All six patients had taken a partly causative medication from different drug classes three to six weeks prior to the start of symptoms and herpes virus was detected in the blood of all of these subjects at the time of DRESS onset (four reactivations and two primary infections), and one patient subsequently displayed herpetic meningoencephalitis 95 days after the initial episode, associated with recurrence of DRESS.

Discussion: There was no common denominator among these six DRESS patients in terms of either drug class or reactivation of a particular type of herpes virus, which raises the possibility of a single unidentified environmental agent. DRESS does not appear fully explainable in terms of a cellular response to drug antigens but seems rather to result from complex interactions between the drug-induced immune response, viral reactivation and antiviral immune response. Several investigators have reported sequential reactivation of herpes viruses in DRESS. A viral epidemic could thus cause a "DRESS epidemic" in patients on medication.

Conclusion: These cases point to the possible existence of a shared initial environmental factor (infectious or not) that favours reactivation of herpes viruses and induces DRESS in patients on medication. Before and after this "DRESS epidemic", about one patient each quarter was admitted to hospital for DRESS.