A 45 year old renal transplant recipient was being evaluated for deteriorating renal function and underwent a renal biopsy. While recovering from the procedure he was observed to be tachypneic prompting investigations including the sputum Gram strain seen below. What is the diagnosis?
GAR was correct again! The image clearly displays yeast cells surrounded by large capsules very suggestive of Cryptococcus spp.. India ink preparations from the same sample showed the typical refractive yeast cells with capsule excluding ink particles.
Typical yeast colonies were visible on blood agar and fungal media within 48 hours. Molecular identification confirmed the identity of the yeast as Cryptococcus gattii.
Xray revealed severe diffuse disease and ICU care was required. Therapy with liposomal amphotericin B and 5-flucytosine was initiated. The patient had been on high dose corticosteroid and other immunosuppressives in a failing effort to stave off rejection.
In North America disease caused by Crytococcus spp. was, until quite recently, found almost exclusively in immunocompromised patients. The species responsible was Crytococcus neoformans – a fungus found in soil around the world with specific association with bird droppings. It was and is a rare but serious cause of pneumonia and meningitis in immunocompromised patients and was particularly problematic during the early days of the HIV AIDS epidemic.
Since 1999 another species of Cryptococcus has been infecting people on Vancouver Island and parts of the Pacific Northwest of Canada and the United States. Cryptococcus gattii is a tree-dwelling fungus that had previously been described as having a predilection for eucalyptus trees and as a rare cause of human infection in endemic areas.
Worldwide interest has been markedly heightened in light of the Vancouver Island situation and it is now clear that the geographic range of C. gattii is quite broad as is the number of species of trees that harbour the fungus. Whether or not the fungus was introduced to Vancouver Island or some other factor (e.g. climactic) was responsible for increase in prevalence is not clear.
While the incidence is low, C. gattii appears to have greater ability to infect immunocompetent people than C. neoformans. It now must be considered a potential pathogen in all patients with lung disease or meningitis that have spent time on Vancouver Island or in other endemic areas prior to their illness.
This case also highlights the ability of C. gattii to cause very severe disease in immunocompromised patients. See BCCDC Crytococcus gattii for further information.