Pneumonia Caused by Mycobacterium shimoidei in a Young Woman with Anorexia Nervosa

Overview

A 37-year-old woman with severe anorexia nervosa and chronic kidney disease developed pneumonia caused by the rare non-tuberculous mycobacterium Mycobacterium shimoidei. Diagnosis was confirmed by next-generation sequencing and culture, and successful treatment was achieved with a tailored 12-month antibiotic regimen.

Background

Mycobacterium shimoidei is a rare non-tuberculous mycobacterium that can cause severe pulmonary infections, particularly in immunocompromised patients. Diagnosis is challenging due to its rarity and similarity to tuberculosis on imaging, requiring microbiological confirmation. Patients with structural lung disease or immunosuppression are at increased risk, but little is known about optimal treatment strategies. This case highlights the diagnostic and therapeutic challenges in managing M. shimoidei pneumonia in a patient with anorexia nervosa and chronic kidney disease.

Data Highlights

Key Findings

• Mycobacterium shimoidei was identified as the causative agent of pneumonia using next-generation sequencing and confirmed by culture.
• The patient presented with multiple cavitary lesions in the left upper lung lobe without prior pulmonary disease history.
• Initial empirical antibiotic therapy was adjusted based on antimicrobial susceptibility testing and renal function, switching clarithromycin to moxifloxacin due to side effect concerns.
• Combination therapy with moxifloxacin, rifabutin, and ethambutol was continued for 12 months with clinical and microbiological improvement.
• Follow-up imaging showed residual lung bulla without active inflammation or progression.
• Severe anorexia nervosa likely contributed to immunosuppression, increasing susceptibility to this rare NTM infection.

Clinical Implications

Clinicians should consider rare non-tuberculous mycobacterial infections like M. shimoidei in patients with immunosuppression and cavitary lung lesions, especially when tuberculosis tests are negative. Next-generation sequencing can facilitate rapid and accurate diagnosis. Tailored antimicrobial therapy adjusted for renal function and nutritional status is critical for successful treatment outcomes.

Conclusion

This case underscores the importance of advanced molecular diagnostics and individualized treatment in managing rare NTM pulmonary infections in immunocompromised patients. Severe anorexia nervosa may be an underrecognized risk factor for such infections.

References

1. Tsukamura et al. 1975 -- First description of Mycobacterium shimoidei
2. Queensland case series 2017 -- Largest published series of M. shimoidei infections
3. Clinical guidelines on NTM pulmonary disease -- Diagnosis and management