Mycobacterium lentiflavum, initially isolated from respiratory samples by Professor Springer in 1996, is a slow-growing, pigment-producing mycobacterium classified as a slow-growing acid-fast bacillus that lacks spores, capsules, or mycelia[6]. Mycobacterium lentiflavum, a rarely encountered species among nontuberculous mycobacteria, mainly affects the lungs causing respiratory-related symptoms. In addition to lung involvement, it frequently affects lymph nodes, leading to lymphadenopathy and lymphadenitis, often depicted on chest CT scans as nodules/bronchiectasis with nonspecific radiological features[7]. The diagnosis of Mycobacterium lentiflavum infection is challenging due to its low culture positivity rate; hence, identification often relies on cultures from affected tissues or secretions and is limited by laboratory conditions and culture techniques, resulting in fewer reported cases. Initially, due to inadequate understanding and nonspecific presentation, Mycobacteria lentiflavum infection was often misdiagnosed as tuberculosis[8]. However, with increasing awareness and advanced diagnostic techniques, especially NGS, more cases have been reported. Cabria Froilán et al[9] reported a case of Mycobacteria lentiflavum infection in a 19-month-old boy with facial lymph node involvement. Jerome Philip et al[10] described a case of Mycobacteria lentiflavum infection in a 5-year-old child affecting the neck and head, along with treatment strategies and literature review. Kentaro Chida etal[11] identified Mycobacteria lentiflavum infection in a lung nodule of a colon cancer patient during follow-up using mass spectrometry analysis of postoperative sputum. Javier Martinez et al[12] reported the first case in which Mycobacteria lentiflavum caused meningitis. Despite the increasing number of reported cases of Mycobacteria lentiflavum infection over the years, a literature review has not identified any reports of this bacterium affecting the nasopharynx. In this case, the patient presented with recurrent rhinorrhea, sensation of nasal foreign body, and multiple instances of nodular erythema on the limbs and experienced multiple misdiagnoses and missed diagnoses in other hospitals, resulting in recurrent clinical symptoms. The correct diagnosis was made only after surgical resection of the nasopharyngeal mass followed by NGS confirmation of Mycobacteria lentiflavum infection. Nodular erythema, traditionally considered a reactive rash, is closely associated with infections and tumors and is commonly attributed to tuberculosis, nontuberculous mycobacteria[13]. The patient's nodular erythema on her limbs suggested a reactive rash following Mycobacteria lentiflavum infection.
In conclusion, due to the rarity of Mycobacterium lentiflavum infection in clinical practice and its nonspecific clinical manifestations, diagnosis has traditionally relied on culture. However, limitations in laboratory conditions and diagnostic techniques often make diagnosis challenging, leading to misdiagnosis by clinicians. Even with a definitive diagnosis, this procedure may take a considerable amount of time. In particular, involvement of the nasopharynx is even rarer. Therefore, when encountering nodules in the lower limbs, confirmed by histopathology as nodular erythema, along with nasopharyngeal symptoms and mass formation, in addition to considering tumors, this possibility should also be taken into account. Apart from improving tissue biopsy for histopathological diagnosis, further refinement of nasopharyngeal tissue culture and NGS is necessary for definitive diagnosis. Currently, there is no specific treatment regimen for this condition. Treatment for slow-growing mycobacteria, including drugs such as clarithromycin or azithromycin, moxifloxacin, rifampicin, ethambutol, doxycycline, etc,often requires requiring combination therapy. Treatment should be continued for at least 1–2 months after skin lesion regression, with a total course of 4–6 months[14]. In this case, the patient was treated with 0.5 g bid clarithromycin, 0.4 g qd moxifloxacin, and 0.45 g qd rifampicin, and after 3 months of treatment, her nasopharyngeal symptoms and nodules in her limbs completely resolved.