Idiopathic thrombocytopenic purpura with brain abscess caused by Nocardia farcinica diagnosed using metagenomics next-generation sequencing of the cerebrospinal fluid: a case report

BACKGROUND: Brain abscesses caused by Nocardia farcinica are rare, and mostly occur in immunocompromised individuals. Rapid and accurate diagnosis of nocardiosis is challenging. Due to the inadequate performance of conventional diagnostic methods for Nocardia infection, metagenomics next-generation sequencing (mNGS) of cerebrospinal fluid (CSF) has the potential to improve the diagnosis intracranial nocardiosis. CASE PRESENTATION: We report a case of 50-year-old man with brain abscess caused by Nocardia farcinica. The patient had a idiopathic thrombocytopenic purpura complication that required long-term methylprednisolone administration. His chest image showed multiple lesions, which had been misdiagnosed as lung cancer, and his head image showed multiple intracranial metastases. No pathogen was detected in routine examinations including blood culture, sputum culture and traditional culture methods of cerebrospinal fluid. In order to accurately identify the pathogen, mNGS was used to detect Nocardia in CSF. Although the patient’s condition improved after using sensitive antibiotics, he transferred to the local hospital for treatment because of many complicated diseases and family financial limitations. CONCLUSION: This case highlights the value of mNGS in the diagnosis of Nocardia brain abscess, and emphasizes the inadequate sensitivity of conventional diagnostic methods for Nocardia infection. Using mNGS can facilitate early and accurate detection of Norcadia-associated of meningitis in immunocompromised patients, thereby reducing unnecessary use of antibiotics and reducing mortality of the disease.