Brucella melitensis infection complicated by secondary hemophagocytic lymphohistiocytosis, meningitis, and multiorgan damage: a case report and literature review.

Background: Brucellosis is one of the most widespread zoonotic diseases globally. Of the twelve known Brucella species that affect mammals, Brucella melitensis is the most significant cause of human infection. Others include B. abortus, B. suis, and B. canis, with transmission occurring via unpasteurized dairy, direct animal contact, or occupational exposure (veterinarians, farmers, and laboratory workers). Although hemophagocytic lymphohistiocytosis (HLH) and neurological complications are known sequelae of brucellosis, their simultaneous occurrence with multiorgan failure is rarely reported.

Case presentation: A 59-year-old female was admitted with dizziness and fatigue for more than 20 days, accompanied by fever and lethargy for 3 days. An epidemiological history revealed that the patient had close contact with goats, which was considered a key risk factor. On physical examination, the patient appeared lethargic, with petechiae on the skin and mucous membranes, oral blood blisters, gingival bleeding, and splenomegaly. Laboratory results revealed significantly increased ferritin levels, decreased fibrinogen levels, pancytopenia, and elevated transaminase levels. Bone marrow aspiration confirmed the presence of hemophagocytes. Cerebrospinal fluid (CSF) examination supported a diagnosis of meningitis. Blood cultures grew Brucella melitensis, and metagenomic next-generation sequencing (mNGS) of CSF revealed a large number of B. melitensis-specific nucleic acid sequences. Chest computed tomography (CT) revealed bilateral pulmonary infiltrates. The patient was ultimately diagnosed with B. melitensis infection complicated by HLH, meningitis, and multiorgan dysfunction. The patient was treated with ceftriaxone sodium, doxycycline, rifampicin, glucocorticoids, and supportive therapy. Following treatment, her consciousness improved, the fever subsided, the total platelet count rose, and liver enzyme levels gradually decreased. The patient was discharged in stable condition. At the 2-month follow-up, the patient remained in remission with normal haematological indicators, no recurrent fever, and stable neurological function.

Conclusions: This case reflects the severe nature of brucellosis when atypical multiorgan involvement is present and highlights the diagnostic challenges and the importance of early and standardized treatment. Maintaining a high level of clinical suspicion and achieving an early definite diagnosis are key to improving treatment outcomes and prognosis. In addition, this case report helps expand the known spectrum of clinical complications related to brucellosis.