Maculopapular Drug Eruption Caused by Apalutamide: Case Report and Review of the Literature.

Apalutamide, an oral androgen receptor signaling inhibitor, is approved for the treatment of non-metastatic castration-resistant prostate cancer and metastatic prostate cancer. In the international randomized placebo-controlled clinical trials, apalutamide was associated with a higher rate of rash than placebo. However, given that reports from a dermatological perspective are limited, the skin manifestations and histopathology of the skin lesions caused by apalutamide are largely unknown. Here, we report a case of apalutamide-induced drug eruption. A 66-year-old man developed itchy maculopapular erythema on the trunk and extremities 10 weeks after starting apalutamide for progressive prostate cancer. A biopsy specimen showed interface dermatitis with perivascular lymphocytic infiltration in the upper dermis. The lymphocyte transformation test was positive for apalutamide. The skin manifestations improved after discontinuation of apalutamide and treatment with topical corticosteroids and systemic prednisolone. A review of the dermatology literature on apalutamide-induced drug eruption yielded only six cases, including our case. Dermatologically, there were four cases of maculopapular rash and two of toxic epidermal necrolysis and histopathologically, there were three cases of interface dermatitis, two of epidermal necrosis, and one of spongiotic dermatitis. Four patients had peripheral eosinophilia. A lymphocyte transformation test was performed in three cases and was positive for apalutamide in all cases. Except for the two cases of toxic epidermal necrolysis, which were fatal, the skin eruptions appeared 10 weeks after starting apalutamide. Considering the increasing number of patients with prostate cancer being treated with apalutamide, cases of apalutamide-induced drug eruption need to be accumulated and analyzed.