Pulmonary sarcoidosis complicated with pulmonary cryptococcosis: a case report

Pulmonary sarcoidosis is an idiopathic granulomatous disorder primarily affecting the lungs and mediastinal lymph nodes. Pulmonary cryptococcosis, an opportunistic mycosis caused by Cryptococcus species, may occur concurrently with sarcoidosis, presenting substantial diagnostic challenges, particularly in treatment-naïve patients. A 63-years-old previously healthy female presented with insidious-onset dyspnea and low-grade fever. Chest computed tomography (CT) showed mediastinal and hilar lymphadenopathy, accompanied by small nodules in the right lower lobe. She was diagnosed with pulmonary sarcoidosis at a local hospital and started on prednisone, with symptomatic improvement. However, follow-up imaging showed enlargement and cavitation of the right lower lobe nodules. Admission laboratory tests, including inflammatory markers and fungal serology, were all unremarkable. Metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid (BALF) identified sequences of Cryptococcus neoformans. Histopathological examination of mediastinal lymph node specimens confirmed the presence of non-necrotizing granulomas, which is consistent with a diagnosis of sarcoidosis. Meanwhile, the right lower lobe lung biopsy revealed positive staining for Cryptococcus. The patient was treated with fluconazole, resulting in radiological resolution. This case highlights the importance of considering pulmonary cryptococcosis as a potential complication in treatment-naïve sarcoidosis patients who present with abnormal chest shadows. Underlying immune dysregulation in sarcoidosis may obscure both clinical and radiological findings, thereby complicating the diagnostic process.