Hemophagocytic lymphohistiocytosis secondary to isolated bronchial infection caused by Mycobacterium marseillense in a patient with GATA2 missense mutation: A rare case report.

BACKGROUND Mycobacterium marseillense is a recently recognized member of the Mycobacterium avium complex, which may be misdiagnosed or overlooked due to its nonspecific clinical manifestations. Few studies on M. marseillense have been reported.

METHODS We report a case of a patient infected with M. marseillense who subsequently developed secondary hemophagocytic lymphohistiocytosis (sHLH). Relevant medical records, including demographic data, medical history, clinical characteristics, laboratory findings, imaging features, treatment regimens, and clinical outcomes, were retrieved from the hospital's unified electronic medical record system and systematically summarized for analysis.

RESULTS A 17-year-old Chinese female was admitted to the hospital due to recurrent fever, cough, and expectoration. Laboratory analyses revealed reductions in white blood cell count, neutrophil count, lymphocyte count, monocyte count, hemoglobin levels, B cell counts, and NK cell counts, as well as decreased natural killer cell activity. Additionally, elevated levels of soluble interleukin-2 receptor, serum ferritin, C-reactive protein, and erythrocyte sedimentation rate were observed. Bone marrow aspiration found hemophagocytic histiocytes. Chest CT demonstrated bronchial stenosis in the right upper lobe with distal occlusion and atelectasis. Fiberoptic bronchoscopy identified a mass completely obstructing the right upper lobe bronchial lumen, with adherent purulent secretions on its surface. Targeted next-generation sequencing was performed on bronchoalveolar lavage fluid samples, and M. marseillense was identified. Following combined treatment with anti-NTM therapy, leucogen and prednisone for sHLH, the patient exhibited clinical improvement and was subsequently discharged from the hospital. After four months of regular therapy, the patient's infectious condition showed improvement upon follow-up evaluation. However, peripheral blood counts of monocytes, B cells, and NK cells remained persistently below the normal reference range. Whole exome sequencing revealed that the patient harbored a GATA2 variant.

CONCLUSIONS Isolated bronchial infections caused by M. marseillense may also lead to sHLH. Although M. marseillense is rare, clinicians should remain vigilant for this potentially severe complication.