Pulmonary cryptococcosis is a fungal infection caused by Cryptococcus neoformans (var gattii or var neoformans). The respiratory tract is the principal route of entry for infection by inhalation of fungal spores. It mostly causes several lung nodules or masses without or with cavitation mostly in immunocompromised patients; besides, consolidation, mediastinal lymphadenopathy and pleural effusion may also be present. Although it is mainly seen in immunocompromised patients, it is also not uncommon in immunocompetent people, in particular, those who are exposed to pigeon and avian droppings.
Cryptococcosis predominantly occurs in immunocompromised patients but can also be seen in the normal host. The spectrum of pulmonary cryptococcosis depends on the host's defenses.
The method of entry is usually by inhalation of cryptococcal particles into the lungs causing pulmonary infection. Spores are found worldwide in soil in which contaminated by avian droppings.
The presentation of pulmonary cryptococcosis can range from asymptomatic nodular disease to severe acute respiratory distress syndrome (ARDS) 3.
In an immunocompetent host the pulmonary infections normally are asymptomatic, different from the immunocompromised patient, in which cryptococcal infections often cause symptomatic infection, often disseminate to the central nervous system, skin, and bones 1:
- approximately one-third of patients are asymptomatic
- symptoms range from mild cough and low-grade fever to acute presentation with high fever and severe shortness of breath 1
Serum cryptococcal antigen (sCRAG) is helpful in diagnosis and follow-up.
In general there are several CT patterns that can be seen:
- clustered nodular pattern: most prevalent 4
- solitary pulmonary nodule or mass with or without cavitation
- scattered nodules
- peribronchovascular consolidation
The most common CT findings in immunocompetent patients with pulmonary cryptococcosis are pulmonary nodules. The nodules are most often multiple, smaller than 10 mm in diameter, and well defined with smooth margins. The nodules usually involve less than 10% of the parenchyma and tend to be distributed peripherally in the middle and upper zones. Where there are multiple nodules, they are usually bilateral 2. Associated cavitation may be seen in up to 40% of cases 8. Occasionally unusual presenation such as large cavities may be seen 13.
FDG PET-CT may play a complementary role to CT 6 and ~ 60% of patients can show higher FDG uptake than the mediastinal blood pool 4.
Treatment and prognosis
Antifungals such as oral fluconazole or intravenous amphotericin B.
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