Pulmonary candidiasis is a form of pulmonary fungal infection and refers to an opportunistic infection of the lung with the fungus Candida albicans. This organism is part of the normal human microbial flora of the oral cavity. Most patients with pulmonary candidiasis tend to have widespread systemic involvement 9.
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Epidemiology
The condition tends to predominate in immunosuppressed patients.
Pathology
As least three characteristic histologic patterns of pulmonary candidiasis have been described 1 :
- embolic (arterial-invasive) pulmonary candidiasis
- disseminated (capillary-invasive) pulmonary candidiasis
- bronchopulmonary (air space-invasive) pulmonary candidiasis
Due to its normal existence within the oral cavity, it is difficult to ascertain whether a positive culture was consistent with a pathogen responsible for pneumonia or whether it occurred as a contaminant. For a definitive diagnosis it has to be confirmed on a open lung biopsy, a transbronchial biopsy, or on autopsy.
Radiographic features
Plain radiograph
The typical radiographic appearance described is progressive air space consolidation: candida pneumonia (which is non-specific). Accompanying focal cavitation may develop. In general, there is thought to be a poor correlation between the radiographic and pathological findings. Often, pathologic findings other than pulmonary candidiasis can account for many of the observed radiological abnormalities.
CT (HRCT) chest
CT features can vary dependant on the pathological pattern and the stage of the disease. Individual features are often non-specific and can be commonly seen in other opportunistic pulmonary infections.
In addition to the above plain film findings (e.g. multifocal airspace opacification without a lobar predilection: candida pneumonia), pulmonary candiasis may also present as pulmonary small pulmonary abscesses or a miliary nodular pattern 7.
The nodular pattern is a common finding, with nodule diameter usually in the range of 3-30 mm. They tend to be multiple. They can be relatively well-defined and can be associated with other parenchymal findings such as air-space consolidation, tree-in-bud changes or ground-glass opacities 4.
In certain cases, a CT halo sign may be seen around the nodular lesions 8.