Metagenomic next-generation sequencing in the diagnosis of leptospirosis presenting as severe diffuse alveolar hemorrhage: a case report and literature review

Background Leptospirosis is a common infectious disease in tropical and semitropical regions, and it is typically neglected. Leptospirosis-associated acute diffuse alveolar hemorrhage is one of its fatal complications. The use of bronchoalveolar lavage fluid (BALF) metagenomic next-generation sequencing in the diagnosis of Leptospira interrogans infection has rarely been reported. Case presentation We present the case of a 62-year-old female who was transferred to our hospital with dyspnea, and severe hemoptysis and was supported by a tracheal intubation ventilator. Bronchoalveolar lavage fluid (BALF) metagenomic next-generation sequencing (mNGS) reported Leptospira interrogans. A diagnosis of diffuse alveolar hemorrhage caused by leptospirosis was made. After immediately receiving antibiotics and hormone therapy, the patient achieved a complete recovery upon discharge. Conclusion Leptospirosis presenting as severe diffuse alveolar hemorrhage is rare but should be considered in the differential diagnosis. mNGS can help identify pathogens and treat them early, which can improve prognosis.