Nasopharyngeal Mycobacterium abscessus Infection: A Case Report and Literature Review.

Background: Mycobacterium abscessus (M. abscessus) is a rapidly growing bacterium (RGM) that causes refractory pulmonary and extrapulmonary infections. However, studies investigating pharyngeal and laryngeal M. abscessus infections are limited. Case Presentation: A 41-year-old immunocompetent woman complaining of bloody sputum was referred to our hospital. Although her sputum culture tested positive for M. abscessus subsp. abscessus, radiological findings were not indicative of pulmonary infection or sinusitis. Further diagnostic workup, including laryngeal endoscopy and positron emission tomography/computed tomography (PET/CT), confirmed the presence of nasopharyngeal M. abscessus infection. The patient was initially treated with intravenous amikacin, imipenem/cilastatin, azithromycin, and clofazimine for 28 days, after which the patient was provided with amikacin, azithromycin, clofazimine, and sitafloxacin for four months. After the completion of antibiotic therapy, the patient showed negative results on sputum smear and culture and normal findings on PET/CT and laryngeal endoscopy. Whole-genome sequencing of this strain revealed that it belonged to the ABS-GL4 cluster, which has a functional erythromycin ribosomal methylase gene, although it is not a major lineage in non-cystic fibrosis (CF) patients in Japan and Taiwan and in CF patients in European countries. We conducted a literature review and identified seven patients who developed pharyngeal/laryngeal non-tuberculous mycobacterium (NTM) infection. Four of the eight patients had a history of immunosuppressant use, including steroids. Seven of the eight patients responded well to their treatment regimens. Conclusion: Patients whose sputum culture tests are positive for NTM and who meet the diagnostic criteria for NTM infection but do not have intrapulmonary lesions should be evaluated for otorhinolaryngological infections. Our case series revealed that immunosuppressant use is a risk factor for pharyngeal/laryngeal NTM infection and that patients with pharyngeal/laryngeal NTM infections respond relatively well to antibiotic therapy.