Lymphadenitis caused by Mycobacterium lentiflavum

Cervical lymphadenitis is the most common infection caused by non-tuberculous mycobacteria (NTM) in immuno-competent children under 5 years. Most cases of NTM associated cervical lymphadenitis worldwide are caused by Mycobacterium avium complex (MAC). Mycobacterium lentiflavum (M. lentiflavum) has been considered a rare cause of NTM associated lymphadenitis. We present two case reports of cervical and pre-auricular lymphadenitis managed in primary care in the Region of Madrid (Spain), between 2019-2020, that persisted despite antibiotic treatment. Routine blood tests, chest x-ray and tuberculin skin test were performed. As NTM was suspected, patients were referred to a tertiary hospital, where they underwent ultrasound guided aspiration, which cultured M. lentiflavum. Although, the first line treatment for NTM lymphadenitis is complete surgical excision, in these cases the proximity of the lymph nodes to the facial nerve and parotid gland meant this was not an option. Instead, a conservative approach of watch-and-wait was chosen in collaboration with the parents, as M. lentiflavum is resistant to most antituberculosis drugs. We conclude that M. lentiflavum should be considered as an important emergent pathogen causing cervical lymphadenitis, especially in cases with a single cervical or pre-auricular lymphadenitis resistant to antibiotic treatment.