Case Presentation: A 70 year-old Moroccan male with a history of gastrointestinal stromal tumor treated with resection and chemotherapy was admitted for dyspnea on exertion and non-productive cough for two weeks. He complained of subjective fevers and weight loss of 47 pounds in 6 months but denied hemoptysis. Lab studies were significant for leukocytosis at 18.77k/ul. Blood cultures and Quantiferon Gold test were negative. CT thorax revealed left upper lobe 6.7cm x 3.8cm cavitary lesion with surrounding inflammation and hilar lymphadenopathy. Gram stain of bronchoalveolar lavage (BAL) showed white blood cells and beaded gram positive rods, acid fast stain showed acid fast bacilli, and culture yielded Mycobacterium abscessus (M. abscessus) only.Patient was treated with combination of azithromycin, imipenem/cilastatin, and trimethoprim/sulfamethoxazole as an inpatient with a plan for prolonged course of the same regimen as an outpatient. Follow up CT scan of the thorax 1 month later showed clinical improvement.
Discussion: M. abscessus is a rapidly growing nontuberculous mycobacterium commonly found in soil and water. It is known for causing skin and subcutaneous infections, primarily in the post-surgical period. However, rarely, it can cause pulmonary infections, mainly in immunocompromised patients. Pulmonary M. abscessus presents clinically similar to other mycobacterium pulmonary infections with cough, fever, and fatigue. CT thorax typically shows cylindrical bronchiectasis and multiple nodules (<5mm). But it can also present as cavitary lesions in less than 15% of cases. Cultures of BAL growing M. abscessus prove the source of infection. It is susceptible to amikacin, imipenem/cilastatin, certain macrolides, sulfamethoxazole, and cefoxitin. Previously, it was thought that local resection of the involved part of the lung combined with antibiotics was the only curative therapy. However, Jeon K et al assert that combination antibiotic therapy alone is moderately effective, albeit, accompanied by adverse reactions. The American Thoracic Society and IDSA recommend combination antibiotic therapy based in a macrolide for disease resolution without lung resection. Combination antibiotic therapy is preferred over monotherapy due to intrinsic resistance of M. abscessus to macrolides alone via erm(41) and rllgene sequences. Lung resection is pursued if patient fails antibiotic treatment.
Conclusions: We presented a case of pulmonary M. abscessus in a patient immunocompromised by chemotherapy putting him at increased risk for atypical infections. Most case reports of pulmonary M. abscessus have occurred in patients with cystic fibrosis or other chronic pulmonary diseases thus making this case an uncommon presentation of an atypical infection. This patient also presented with the less common finding of cavitary lesions along with showing improvement with combination antibiotic therapy without surgical intervention.