Not All Infectious Cavitary Lesions Are Due to Tuberculosis

Abstract

Introduction: Cavitary lung lesions can be caused by malignancy, infection, and inflammatory disorders. Among infectious etiologies mycobacterium and fungal infections are the most common causes but pseudomonas aeruginosa can also cause cavitary lung infection. We present a case of cavitary lung infection caused by pseudomonas aeruginosa. Case: A 70 years old women with a history of frontal lobe glioblastoma status post resection presented with a 1-week history of productive cough with yellow green sputum production. She had been receiving dexamethasone and radiotherapy prior to admission. She was tachypneic with a respiratory rate of 21 breaths per minute, oxygen saturation was 94% on 2 liters oxygen. Lung exam revealed right sided crackles. Labs including CBC, CMP, HIV and procalcitonin were normal. X-Ray of her chest showed patchy opacity in the right midlung concerning for infection. CT scan of the chest showed right upper lobe cavitary disease, bronchitis and bronchiolitis that was not present on any prior imaging. The patient was started on antibiotics and underwent work up for the etiology of the cavitary lung lesion. Sputum AFB smear was negative 3 times. Respiratory viral panel and COVID 19 testing were negative along with urinary antigens for streptococcus pneumoniae and legionella. Aspergillus galactomannan and cryptococcal antigen were also negative. Sputum culture and sensitivity showed pseudomonas aeruginosa. The patient's cavitary lesion was considered to be secondary to pseudomonas aeruginosa as it can cause cavitary lesions in immunocompromised patients. Our patient was on steroids for glioblastoma which made her prone to the development of the cavitary lesion. She was treated with cefepime and showed significant clinical improvement. She will receive a total of 3 weeks of antibiotics with a follow up CT scan to confirm improvement prior to stopping antibiotics. Discussion: Pseudomonas is a gram-negative rod that is a rare cause of community acquired pneumonia. Risk factors for pseudomonas lung infections include immunosuppression and structural lung abnormalities such as Cystic Fibrosis. Even more rarely, Pseudomonas has been reported in the literature as a cause of cavitary lesions. Pseudomonas can cause cavitation due to parenchymal necrosis. Parenchymal necrosis is driven by the exuberant inflammatory response. Our patient was on high doses of dexamethasone making her immunocompromised and prone to cavitary lung lesions. Treatment with antipseudomonal antibiotics with follow up imaging to ascertain resolution is the gold standard.