DRESS syndrome in a patient undergoing stem cell transplantation: Can sirolimus be involved?

We present a case of sirolimus-induced drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome in a stem cell transplant patient. Sirolimus is an immunosuppressive drug that inhibits the mammalian target of rapamycin (mTOR) pathway. A 24-year-old male with a history of acute lymphoblastic leukemia (ALL) underwent testicular extraction followed by hematopoietic stem cell transplantation (HSCT). He presented with pruritic eczematous lesions, which were initially treated with topical steroids. However, he later developed diffuse xerosis, fever, chills, generalized edema, weight gain, eosinophilia, and leukopenia. Skin biopsy showed spongiotic dermatitis with eosinophils, suggesting a drug or atopic reaction. Investigations ruled out infections, and the RegiSCAR score indicated drug reaction syndrome with eosinophilia and systemic symptoms (DRESS). Sirolimus, an immunosuppressive drug, was suspected as the cause. Sirolimus was discontinued, and oral steroids were initiated. After 3 weeks of therapy, the patient showed improvement with resolution of symptoms. Although no cases of sirolimus-induced DRESS syndrome have been reported, allergic reactions with eosinophilia induced by everolimus have been documented. In our case, the patient's history characterized by stem cell transplantation and multiple immunosuppressive therapies may have contributed to the development of DRESS syndrome after beginning sirolimus therapy. This case may be the first evidence of sirolimus-induced DRESS syndrome in a stem cell transplant patient.