Cryptococcosis

Approximately one million new cases of cryptococcosis develop each year worldwide, resulting in approximately 600,000 deaths. Most cases occurred in HIV patients from African countries south of the Sahara Desert. In light of this situation, in 2022, the World Health Organization presented a list of priority fungal pathogens to guide research, development, and public health action, with Cryptococcus neoformans as the most important critical fungus. In contrast, a recent retrospective study in developed countries showed that 90% of cases with cryptococcosis were non-HIV patients, including immunocompetent individuals. Underlying diseases of non-HIV immunocompromised patients include cancer and solid organ transplantation. High serum titers cryptococcal antigens independently predicted the risk of central nervous system involvement. Even if the patient is asymptomatic, high antigen levels are considered a possibility of cryptococcal meningitis, and a spinal fluid examination may be recommended. The absence of a history of contact with pigeons should not be used as a basis for denying cryptococcosis because C. neoformans is often detected in old and dried feces of chickens other than pigeons. Donor-derived cryptococcosis is a unique feature of cryptococcosis in solid organ transplant recipients. Pre-transplant screening tests for cryptococcosis, pre-transplant treatment for the donor, and prophylactic antifungal therapy for the recipient may be useful. Defense against cryptococcal infection is regulated by various mechanisms, including Th1, Th2, and Th17 immune responses. Molecularly targeted medicines that target specific cytokines or surface antigen molecules have been widely used with excellent clinical efficacy for the treatment of various diseases. Since cryptococcosis has been recently reported to develop during the use of certain medicines, such as ibrutinib and eculizumab, clinicians need to be mindful that the number of similar cases may increase in the future.