Pulmonary Abscess Caused by Neisseria meningitidis: A Case Report.

Neisseria meningitidis is a Gram-negative diplococcus commonly associated with meningitis or septicemia. However, it may rarely cause pulmonary abscesses, particularly in adults with risk factors such as smoking, chronic alcoholism, or underlying lung disease. The differential diagnosis should include other bacterial etiologies, and laboratory confirmation is essential. Recognition of atypical pulmonary presentations is crucial for appropriate management and mandatory reporting, given the potential for severe progression and the need for chemoprophylaxis among contacts. We report the case of a 60-year-old male, active smoker and chronic alcohol consumer, with a previous history of upper gastrointestinal bleeding requiring antrectomy. The patient presented with six months of anorexia and asthenia, melena of 15 days' duration, and worsening chronic cough. Laboratory findings revealed macrocytic hypochromic anemia, mild hyponatremia, and elevated inflammatory markers. Thoracic CT showed a thick-walled, cavitated mass in the middle lobe suggestive of malignancy. During hospitalization, the patient developed a fever. Bronchoscopy showed purulent, foul-smelling secretions at the middle lobe bronchial emergence. Microbiological analysis of bronchial secretions identified N. meningitidis. Directed therapy with intravenous ciprofloxacin (400 mg every eight hours) was initiated, and the patient was maintained under contact isolation, with subsequent clinical and laboratory improvement. Lung abscesses caused by N. meningitidis are a rare clinical entity, with few cases described in the literature; meningeal or septicemic involvement is far more common. This case underscores the need to considerN. meningitidis in the differential diagnosis of cavitary pulmonary lesions, particularly in patients with risk factors such as chronic smoking and alcoholism. The clinical presentation may mimic lung cancer or abscess, and identification requires microbiological confirmation from sputum or bronchoalveolar lavage samples. Prompt recognition is essential for adequate antibiotic therapy and public health measures. This case highlights the importance of considering N. meningitidis in the differential diagnosis of cavitary lung lesions, reinforcing the need for microbiological surveillance, multidisciplinary management, and targeted therapy.