Pulmonary Cryptococcosis

Abstract

Pulmonary cryptococcosis describes an invasive lung mycosis caused by Cryptococcus neoformans or Cryptococcus gattii complex. It is often a high-consequence disease in both immunocompromised and immunocompetent populations, and may be misdiagnosed as pulmonary malignancy, leading to a delay in therapy. Epidemiology follows that of cryptococcal meningoencephalitis, with C. gattii infection more common in certain geographic regions. Diagnostic tools include histopathology, microscopy and culture, and the detection of cryptococcal polysaccharide antigen or Cryptococcus-derived nucleic acids. All patients with lung cryptococcosis should have a lumbar puncture and cerebral imaging to exclude central nervous system disease. Radiology is key, both as an adjunct to laboratory testing and as the initial means of detection in asymptomatic patients or those with non-specific symptoms. Pulmonary cryptococcomas (single or multiple) may also be associated with disseminated disease and/or cryptococcal meningitis, requiring prolonged treatment regimens. Optimal management for severe disease requires extended induction (amphotericin B and flucytosine) and consolidation therapy (fluconazole) with close clinical monitoring. Susceptibility testing is of value for epidemiology and in regions where relatively high minimum inhibitory concentrations to azoles (particularly fluconazole) have been noted. Novel diagnostic tools and therapeutic agents promise to improve the detection and treatment of cryptococcosis, particularly in low-income settings where the disease burden is high.

Keywords: antifungal agents; cryptococcosis; diagnosis; immunosuppression.

Figure 1

Geographical distribution of the major molecular types within the Cryptococcus neoformans and Cryptococcus gattii species complexes. Authors’ adaptation from [25].

Figure 2

Representative (A) chest X-ray showing pulmonary Cryptococcus gattii infection with associated Pancoast syndrome (adapted from [33] by courtesy of Oxford Academic); (B) chest high-resolution computed tomography image of a pulmonary cryptococcoma (axial view); (C) India ink stain of Cryptococcus spp.; (D) periodic acid-Schiff and (E) mucicarmine stains of lung tissue with Cryptococcus spp. seen (with capsule staining bright pink in colour).