Cryptococcosis

In this lung section one sees numerous cryptococcal organisms. The surrounding halo is partially due to shrinkage artifact but also includes space occupied by the non-staining capsule of this yeast. Humans are exposed to this organism by inhalation of the organism from dried bird droppings.

The organism is stained red in this periodic-acid-Schiff stained section. The capsule does not stain. The cryptococcus usually gains entry via the respiratory tract. Sometimes pneumonia is not evident clinically and the patient presents later with meningitis.

In this mucicarmine-stained section the organism is red. It appears larger than on the previous slide because of staining of the capsule.

Though there are several species of cryptococcal organisms, the one which is prominent as a pathogen in humans is C. neoformans. Cryptococcal disease was rare until after the 1940s. It is one of the secondary diseases which has become prominent since the advent of AIDS. Even before the 1980s, however, it was being noted in patients on steroids and patients with other immunodeficiency states. Cryptococcosis can involve almost any organ in the body but the lung and central nervous system are most likely to be the sites of significant disease. The organism usually enters the body via inhalation from bird droppings. In immunocompetent individuals the lung involvement may be asymptomatic and the organism goes no further; the yeast is readily phagocytized and destroyed, especially if unencapsulated. Human to human transmission does not occur except via organ transplantation. Pulmonary cryptococcosis is variable in its clinical manifestations from asymptomatic colonization to acute respiratory distress syndrome. CNS involvement is usually in the form of meningitis or meningoencephalitis. Diagnosis can be made by identifying the organism in cerebrospinal fluid, sputum, urine, or tissue. Latex agglutination tests of serum or CSF are also of value. Amphotericin B is the initial treatment of choice.