Case Report: Refractory Cryptosporidiosis after CAR T-Cell Therapy for Lymphoma.

Cryptosporidial diarrhea is uncommon in immunocompetent individuals, more often seen in severely immunocompromised patients. Severe refractory cases have been described in patients with HIV/AIDS before the advent of modern antiretroviral therapy due to an inability to mount an adequate cellular immune response. We describe an 85-year-old patient post-chimeric antigen receptor T-cell therapy relapsed lymphoma who developed refractory Cryptosporidium spp. diarrhea in the setting of persistent CD4+ cytopenia. Despite receiving multiple antiparasitic agents, including failure of a prolonged course of nitazoxanide, the patient experienced persistent symptoms for 9 months with repeatedly positivity stool Cryptosporidium spp. direct fluorescent antibody (DFA) test. We highlight this case of refractory Cryptosporidium spp. and the importance of recognizing the pathogen in a non-HIV-infected immunosuppressed host.