Background:

Cryptococcus neoformans (C. neoformans) is commonly presented in immunocompromised individuals and causes cryptococcosis mostly in the respiratory and/or central nervous system. Liver cryptococcosis is exceedingly rare and sometimes difficult to diagnose through conventional assays.
Case presentation:
The present study reports a rare case of liver cryptococcosis characterized by increased serum carbohydrate antigen 19-9 (CA19-9) level and intrahepatic multiple nodules without other symptoms in an immunocompetent woman. Her cancer family history and imaging examinations initially suspected metastatic liver malignancy. But no sign of the malignant tumor was found after endoscopy, 18-fluorine fluorodeoxyglucose positron emission tomography-computed tomography, and liver biopsy. The histopathology of the liver biopsy specimen indicated chronic inflammatory granuloma and then infectious diseases were suspected. However, traditional microbiologic testing failed to identify any potential pathogen. Eventually, metagenomic next-generation sequencing (mNGS) was applied to identify the definite diagnosis of liver cryptococcosis by acquiring the genome sequence of C. neoformans. Fortunately, after 6-month diagnostic anti-fungal therapy of fluconazole, the liver nodules effectively faded away and the serum CA19-9 level gradually regressed to the normal range.
Conclusion:
We identified a rare case of hepatic cryptococcosis by mNGS in an immunocompetent patient. When conventional methods have difficulties in the diagnosis of a specific pathogen, mNGS has the advantage of early and accurate identification of potential pathogens from the specimen.