Concurrent Brucellosis and Acute Lymphoblastic Leukemia: A Case Report.

Introduction: Acute lymphoblastic leukemia (ALL) is a rare hematologic malignancy that leads to significant qualitative and quantitative lymphocyte deficits. These immunological gaps predispose patients to various bacterial and opportunistic infections. Brucellosis, an intracellular infection endemic in many regions including Iran, presents with nonspecific symptoms such as prolonged fever, malaise, and organomegaly, which closely mimic the clinical manifestations of leukemia. Their co-occurrence, even in brucellosis-endemic areas, is actually rare. In addition, their similarity in clinical presentation can result in diagnostic delay or misdiagnosis. Case Presentation: A 47-year-old male shepherd from an endemic region in Iran presented with a 1-month history of progressive weight loss, fever (38.4°C), and muscle cramps. Initial physical examination revealed pallor and tachycardia without lymphadenopathy. Laboratory investigations showed severe leukocytosis (103 × 10 Conclusion: This case highlights the importance of considering brucellosis in the differential diagnosis of febrile patients with hematologic malignancies in endemic areas. Overlapping symptoms can lead to diagnostic delays. It is crucial to repeat serological tests or use serial dilutions to circumvent the prozone effect when clinical suspicion persists in immunocompromised patients.