Is pulmonary cryptococcosis a unique pathology?

We read with great interest the well-written manuscript by Hu et al. [1], who reported pulmonary cryptococcosis (PC) in China. They reported that solitary cavitary pulmonary nodule may be a common computed tomography fi nding in AIDSassociated PC. However, we would like highlight some important aspects. Cryptococcus neoformans was fi rst isolated in 1894 from fermented peach juice by the Italian Francesco Sanfelice [2]. Since that time, this organism has been recovered from numerous locations throughout the world, where its main ecological niche is soil, particularly in association with pigeon excreta [3]. Cryptococci grow as unicellular, encapsulated cells in the asexual state, or as basidiomycetous fi laments in the sexual state [2]. Infection due to this opportunistic fungus is believed to occur by inhalation and primarily targets the lung, with frequent dissemination to the central nervous system, as well as a variety of other organs [2]. Cryptococcus gattii was fi rst isolated from a leukemic patient in 1970 and described as a variant of C. neoformans [4]. However, C. gattii (formerly Cryptococcus neoformans var. gattii) [2] is a basidiomycetous yeast that is pathogenic to immunocompetent mammals including humans. This relatively uncommon organism differs from the congeneric, more commonly encountered pathogen C. neoformans, with regards to phenotypic characteristics, natural habitat, epidemiology, ecology, clinical manifestations of disease, and responses to antifungal therapy [5]. Phylogenetic studies have shown that C. gattii and C. neoformans diverged from a common ancestor approximately 40 million years ago [3]. C. gattii has the ability to inhibit polymorphonuclear leukocyte (PMN) migration to the site of the organism [2,3], which may promote survival of the extracellular organisms, and can multiply locally to form cryptococcomas that can potentially be misdiagnosed as malignancies [1 – 4]. Compared to C. neoformans, C. gattii infections more often cause granulomatous lesions (cryptococcomas) in the lung and brain, with more associated neurological sequelae and morbidity [6 – 9]. Because of these data, we do not believe that pulmonary cryptococcosis can only be regarded as a unique pathology.