Cryptococcosis and other rare invasive yeasts infections

Although Candida spp. are the most common cause of invasive fungal infection in immunocompromised patients, a variety of other yeasts also cause disease in this cohort. Early recognition of these infections, along with appropriate antifungal therapy, supportive care, and source control (as possible), are essential to limiting the host damage caused by these infections. This chapter includes a review of disease caused by Cryptococcus neoformans, the most common cause of fungal meningitis. Cryptococcosis occurs in a wide variety of immunocompromised hosts but has become particularly problematic for solid organ transplant recipients. The meningoencephalitis caused by C. neoformans is typically subacute and associated with increased intracranial pressure, which if not adequately addressed contributes significantly to the mortality of this disease. Combination antifungal therapy with amphotericin and flucytosine has been shown to provide more rapid sterilization and improved outcome compared with amphotericin alone. Immune reconstitution inflammatory syndrome in association with cryptococcosis occurs as a result of an exuberant inflammatory response. Immune reconstitution inflammatory syndrome can result in exacerbation of disease symptoms and loss of graft function. The other invasive yeast infections reviewed in this chapter cause a minority of fungemias in immunocompromised hosts. However, the mortality of these infections can be quite high. These yeasts tend to be colonizers, causing disease (especially central line infections) in the appropriate clinical context. Risk factors for these infections are similar to those of invasive candidal infection and include both neutropenia as well as ongoing antibiotic exposure. These yeasts tend to have intrinsic antifungal resistance, especially to the echinocandins, and infections often arise in patients receiving antifungal therapy for other reasons.