Leptospirosis presenting with fever, jaundice, and generalized lymphadenopathy: a case report with diagnostic challenges.

Introduction and Importance: Leptospirosis is a widespread zoonotic infection caused by Case Presentation: A 30-year-old male farmer from Rustam, with a prior history of atrial fibrillation, presented to Mardan Medical Complex with a 20-day history of high-grade intermittent fever, body aches, and headaches, along with recent-onset left flank pain, burning micturition, and dry cough. Clinical examination revealed fever, mild jaundice, and tender inguinal and cervical lymphadenopathy. Lab investigations showed microcytic anemia, thrombocytopenia, elevated liver enzymes, and mild pyuria. Imaging revealed splenomegaly and mild pleural effusion. Excisional lymph node biopsy showed histiocytes with organisms suggestive of Clinical Discussion: Acute leptospirosis was confirmed by histopathological findings on lymph node biopsy and positive Leptospira-specific IgM serology. This case highlights a rare presentation of leptospirosis mimicking hematological malignancy, with lymphadenopathy and systemic symptoms initially raising suspicion for lymphoma. Diagnosis was established through lymph node biopsy, which is uncommon in leptospirosis workup, and later confirmed serologically. The case underscores the importance of considering leptospirosis in the differential diagnosis of febrile illnesses with lymphadenopathy, especially in endemic regions, and demonstrates the diagnostic value of histopathology when routine investigations are inconclusive. Conclusion: Early recognition of atypical leptospirosis presentations is crucial to avoid misdiagnosis. Histopathology can aid diagnosis where advanced testing is unavailable, emphasizing the need for a multidisciplinary approach in resource-limited settings.