Severe Cryptosporidiosis Following Tumor-Infiltrating Lymphocyte Therapy in a Patient With Metastatic Mucosal Melanoma

Cryptosporidium is a protozoan parasite that can cause respiratory and gastrointestinal illnesses with watery diarrhea. Severe disease may occur in immunocompromised patients, especially those with acquired immunodeficiency syndrome or metastatic mucosal melanoma on immunosuppressive therapy. We report a 72-year-old man with metastatic mucosal melanoma treated with surgery, radiation, and tumor-infiltrating lymphocytes therapy complicated by hemophagocytic lymphohistiocytosis and autoimmune colitis. He presented with an acute profuse diarrhea despite sulfasalazine and budesonide therapy for his colitis. Intestinal biopsy confirmed Cryptosporidium parvum. Although uncommon, cryptosporidial infection should be suspected in immunocompromised patients with persistent diarrhea. Diagnosis is via stool microscopy, polymerase chain reaction, or enzyme immunoassay.