A case of pulmonary cryptococcosis caused by capsule-deficient cryptococcus neoformans in an immunocompetent patient.

Cryptococcus neoformans is a common cause of opportunistic infection in patients with human immunodeficiency virus (HIV) and others with cell-mediated immunodeficiency, such as patients with solid-organ-transplant-related immunosuppression, patients receiving corticosteroids or other immunosuppressive therapy, and patients with lymphoid malignancy.1,2 The central nervous system (CNS) is the most common clinically relevant site of cryptococcal infection, and meningoencephalitis is the most frequently encountered manifestation. Also, most of the morbidity and mortality due to cryptococcosis results from its CNS involvement. The pulmonary system is the second important site of infection, as reported by a study of 306 HIVnegative patients with cryptococcosis, which found CNS involvement in 157 patients and pulmonary involvement in 109 patients.3 Most immunocompetent patients with pulmonary cryptococcosis are symptomatic, and the most common presenting symptoms are cough, dyspnea, and fever.3-5 The most common radiological finding in pulmonary cryptococcosis is well defined solitary or multiple pulmonary nodules.5,6 The capsule of Cryptococcus neoformans has antiphagocytic properties and is an important virulence determinant.7 Infection by a capsule-deficient strain of Cryptococcus neoformans is rare in immunocompromised patients and even rarer among immunocompetent patients. We present a case of pulmonary cryptococcosis caused by capsule-deficient Cryptococcus neoformans in an immunocompetent patient, discovered incidentally during the diagnosis of bilateral pulmonary nodules resembling metastatic lung cancer. Case Summary