Atypical Legionella pneumonia in Geriatric Practice: Diagnostic complexity and domestic hot tub as source of infection.

Background: Legionnaires’ disease, a form of atypical pneumonia caused by Legionella pneumophila, can present without respiratory symptoms, particularly in elderly patients with multiple comorbidities. While commonly associated with contaminated water sources and travel-related exposure, community-acquired cases without typical respiratory symptoms can be easily overlooked. Early recognition and targeted therapy are crucial to reduce morbidity and mortality. 

Case Presentation:A 78-year-old male, ex-smoker, with known COPD, Chronic kidney Disease, non-alcoholic fatty liver disease and hypertension presented with fever, confusion, diarrhea, vomiting, and headache, but no cough, chest pain, or dyspnea. His atypical presentation prompted a broad initial workup. On admission, he was febrile, disoriented, and hemodynamically stable. His CURB-65 score was 3, indicating a high risk of mortality from pneumonia. A 4AT score of 6 suggested delirium, consistent with his acute confusion. 

Investigation & Management:Blood tests showed leukocytosis (WCC 13.4 × 10⁹/L) and a markedly raised CRP (349 mg/L). Blood cultures remained negative. Chest X-ray revealed extensive left upper lobe consolidation and right lower lobe involvement. Initial management included IV piperacillin-tazobactam for presumed sepsis.Upon radiological findings, empirical amoxicillin and clarithromycin were commenced for CAP. A positive Legionella urinary antigen test and confirmatory PCR for L. pneumophila serogroup 1 prompted a switch to oral levofloxacin, completed over 10 days. The patient made a full recovery and was discharged with plans for follow-up imaging in six weeks. 

Conclusion:This case underscores the importance of suspecting Legionnaires’ disease in elderly patients with systemic symptoms and radiographic pneumonia—even in the absence of respiratory complaints. A high index of suspicion, combined with rapid diagnostic tools, can guide targeted therapy. Notably, the source was traced to a home hot tub—highlighting how domestic exposures, not just travel, can be culprits in atypical pneumonia. As a notifiable disease, this case was reported to public health authorities to support surveillance and prevention efforts.