Study of the clonality of cutaneous and blood lymphocytes during drug-induced hypersensitivity in 6 patients

Introduction. The drug-induced hypersensitivity syndrome or DRESS (drug reaction with eosinophilia and systemic symptoms) is a severe toxiderma because it is accompanied by lethal visceral involvement in 6 to 10% of cases. Its physiopathology remains unclear. In order to specify the immunological characteristics of this toxiderma we analyzed, prospectively, the rearrangement of the blood and cutaneous T-cell lymphocyte receptor (TCR) genes of patients exhibiting a drug-induced hypersensitivity syndrome between April 1998 and April 2000. Patients and methods. The inclusion criteria were age over 18 years, occurrence of a drug-induced generalized eruption, existence of associated systemic involvement (lymph node or visceral) and presence of hypereosinophilia greater than 0.5 G/I and/or circulating atypical lymphocytes. Six patients (3 men and 3 women), with a mean of 54 years were included. The imputable drug was an anti-seizure in 3 cases, allopurinol in 2 and oxazepam in one. Remission occurred within a delay of 10 to 30 days after the acute phase. Two patients presented several flares. Results. No clonal rearrangement in TCR genes was detected in the cutaneous samples. A clonal rearrangement of TCR genes was initially detected in the blood lymphocytes of 3 out of the 6 patients (allopurinol: n=2 and oxazepam: n=1). The latter remained detectable during the evolution, during the second or third flare of the drug-induced hypersensitivity in 2 patients (allopurinol: n=1 and oxazepam n=1). Discussion. The presence of circulating T-cell Bones detectable for several months after the occurrence of a drug-induced hypersensitivity shows the mono or oligoclonal expansion of activated T-cells, induced by the drug imputed. Their persistence over several months corresponds to a remnant activation of the immune system that can explain the prolonged and/or recurrent evolution of the drug-induced hypersensitivity syndrome in some patients.