ATYPICAL PRESENTATION OF LEGIONNAIRES DISEASE WITH DIVERTICULITIS IN IMMUNOSUPPRESSED PATIENT

ABSTRACT

CASE A 69-year-old male smoker with stage 3b prostate cancer managed with abiraterone and prednisone, prior severe COVID-19 pneumonia requiring mechanical ventilation, and history of perforated sigmoid diverticulitis presented with 3 days of anorexia, watery diarrhea, and left lower abdominal pain. Two weeks earlier he developed a mild dry cough without fever, dyspnea, or chest pain. There were no sick contacts or recent travel. He was afebrile, and initial routine chemistries and a complete blood count were unremarkable. An abdomino-pelvic CT revealed acute diverticulitis of the distal descending and sigmoid colon. A consolidation at the right lung base was also incidentally noted. Follow up imaging confirmed a multifocal pneumonia on chest Xray. Legionella antigen was detected in the urine. Metronidazole and levofloxacin were initiated with clinical improvement and the patient was discharged home to complete a 10-day course of antibiotics IMPACT/DISCUSSION: Legionella bacteria are gram negative organisms found widespread in soil and bodies of water including lakes, streams, and artificial reservoirs. Transmission is via inhalation of aerosols and a high innoculum is typically needed to cause infection. Host risk factors for infection include older age, impaired cellular immunity, smoking, male sex, and medical co-morbidities such as diabetes mellitus, renal, lung and cardiovascular disease. The two most commonly known syndromes associated with Legionella infection are Legionnaire's disease, a pneumonia occurring typically in the late summer or early autumn months (as in our patient), and Pontiac fever, an acute self- limited febrile illness. The mortality rate for hospitalized Legionnaire's is up to 10%. Extra-pulmonary manifestations are rare and can include skin and soft tissue infections, septic arthritis, endocarditis, myocarditis, peritonitis, pyelonephritis, meningitis, brain abscesses, and surgical site infections. The diagnosis of extra-pulmonary disease requires detection of Legionella at the affected site by culture or polymerase chain reaction. In the absence of a known local Legionella outbreak, our patient's age, sex, smoking status, and underlying immune suppression most likely increased his risk for this sporadic infection. We postulate that the acute diarrhea associated with Legionnaire's disease may have triggered inflammation of his diverticula or the acute diverticulitis was an extra-pulmonary manifestation. To our knowledge, we are the first to report a case of Legionnaire's disease presenting as acute diverticulitis. CONCLUSION: Legionnaire's is a typical disease with many atypical and extra-pulmonary presentations. We present a case of Legionnaire's disease masquerading as acute diverticulitis and urge timely consideration and testing for Legionella in at-risk patients presenting with predominantly GI symptoms and subtle or no respiratory complaints, as it can be life-saving.