The diagnosis of scabies can be difficult when the infection presents as erythroderma. Crusted scabies is a severe form of scabies caused by cutaneous ectoparasitic infection by the mite Sarcoptes scabiei var hominis. Crusted scabies most commonly occurs in patients with underlying immunosuppression from acquired infection or subsequent to solid organ or bone marrow transplantation. We present a rare case of a patient with granulomatosis with polyangiitis (GPA) who developed azathioprine-induced myelosuppression and subsequent erythrodermic crusted scabies. It is critical to maintain a broad differential when patients present with erythroderma, especially in the setting of medication-induced immunosuppression for the treatment of autoimmune disease.