Cryptococcosis

What is Cryptococcosis?

Cryptococcosis is acquired through inhalation of Cryptococcus spp. spores in the environment, including soil, bird excreta and decaying wood.¹ Cryptococcus neoformans is mainly associated with infections in immunocompromised patients and C. gattii is mainly associated with infections in immunocompetent individuals.^1,2

Pathogenesis

Cryptococcosis initially affects the lungs, but can disseminate to other parts of the body, including the central nervous system, skin, prostate and eyes.¹ Cryptococcus spp. can establish latent infection in alveolar macrophages, which can persist asymptomatically.¹ Host immunosuppression can allow the fungi to disseminate and reactivate infection.¹

Epidemiology

In 2020, the annual global incidence of cryptococcal meningitis was estimated at 152,000 cases per year and cryptococcal deaths (among those with diagnosed meningitis as well as those without overt meningitis) were estimated at 112,000 per year.³ The majority of these cases (54%) and deaths (63%) occurred in Sub-Saharan Africa.³

In terms of global distribution, C. neoformans is found worldwide, whereas C. gattii is endemic to Australia, Papua New Guinea and the Pacific Northwest region of North America.⁴

C. neoformans cryptococcosis is a very serious disease, with mortality rates ranging from 41 to 61%, especially in patients with human immunodeficiency virus (HIV) infection.⁵ Median hospital length of stay in patients with C. neoformans infection ranged from 18 to 39 days, predominantly reported in patients who were HIV positive.⁵

Risk factors

HIV infection/acquired immunodeficiency syndrome (AIDS) is a leading risk factor for cryptococcal infection, with cryptococcal disease accounting for 19% of AIDS-related deaths globally.^3,5

Other conditions in which the host immune system is suppressed are also associated with infection, including:⁵

• Iatrogenic immunosuppression (e.g., corticosteroid use)
• Autoimmune disease
• Organ transplant recipients
• Decompensated liver cirrhosis

Pathogenic species

• C. neoformans and C. gattii are the species most commonly associated with causing disease in humans; the majority of cryptococcal infections are caused by C. neoformans, although C. gattii is more likely to cause infection in immunocompetent hosts^1,2
• Other pathogenic Cryptococcus spp. include C. laurentii, C. uniguttulatus, C. luteolus and C. albidus⁶