Multiple drug sensitization syndrome: A distinct phenotype associated with unrecognized Mycoplasma pneumonia infection

ADRs: adverse drug reactions LTT: lymphocyte transformation test MDH: multiple drug hypersensitivity MDHS: multiple drug hypersensitivity syndrome MP: Mycoplasma pneumoniae PA: particle agglutination SJS/TEN: Stevens-Johnson syndrome/toxic epidermal necrolysis Tregs: regulatory T cells INTRODUCTION Many adverse drug reactions (ADRs), including Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), are thought to be caused by delayed-type, cell-mediated immune reactions to a single drug or its related compounds. The term multiple drug hypersensitivity syndrome (MDHS) has been used to describe patients who show delayed-type, cell-mediated immune reactions to 2 or more chemically distinct drugs. Despite the seemingly low prevalence of MDHS, these cases pose the fear of progressing to more severe and widespread forms of ADRs unless the culprit drugs are withdrawn. Thus, it is important to identify patient factors that could increase the risk of multiple drug hypersensitivity (MDH). Although MDHS was initially defined based on a detailed case history alone or skin tests, a recent study clearly shows that MDHS can be most efficiently proven by an in vitro lymphocyte transformation test (LTT). Interestingly, sporadic case reports described that MDH or drug reactions were observed associated with Mycoplasma pneumoniae (MP) infection. Indeed, there is mounting evidence suggesting that such infections create a favorable milieu for the initiation and progression of ADRs by abrogating regulatory T-cell (Treg) function.