Diagnostic and Therapeutic Challenges in Disseminated Mycobacterium colombiense Infection Caused by Interferon-γ Neutralizing Autoantibodies.

Adult-onset immunodeficiency due to interferon-γ-neutralizing autoantibodies (nIFNγ-autoAbs) can remain underdiagnosed. We present a case of severe Mycobacterium colombiense infection with nIFNγ-autoAbs. To ensure early diagnosis, clinicians should have a high index of suspicion in patients of Asian descent with opportunistic infections and perform QuantiFERON-TB assay for disease screening.

A non-immunocompromised host with nontuberculous mycobacteria-associated tubulointerstitial nephritis.

A 50-year-old man was admitted to our hospital with the complaints of fever and general malaise. He had no history of human immunodeficiency virus (HIV) infection or treatment with immunosuppressive agents. We performed renal biopsy to investigate possible acute kidney injury. Pathological findings showed inflammatory cell infiltration, including granulomatous lesions in the interstitium. We diagnosed the patient with acute granulomatous tubulointerstitial nephritis. We initiated prednisolone (PSL) 40 mg/day (0.6 mg/kg), in combination with isoniazid for a latent tuberculosis infection, because of positive results in interferon-γ release assays. The patient's fever and malaise promptly disappeared, and his renal function improved. After the patient had been discharged, Mycobacterium intracellulare grew in cultures of his renal tissue and urine. We gradually reduced the dose of PSL; we initiated combination therapy with ethambutol, clarithromycin, and rifampin. After 2 years of follow-up, the patient continued treatment for chronic kidney disease; it has since enabled him to avoid renal replacement therapy. This report describes a rare instance of nontuberculous mycobacteria-associated tubulointerstitial nephritis in a patient without a history of HIV infection or organ transplantation. In differential diagnosis of granulomatous tubulointerstitial nephritis, clinicians should consider drugs, sarcoidosis, tubulointerstitial nephritis and uveitis syndrome, vasculitis, and infections (e.g., involving mycobacteria). Prompt microbiological examinations, especially of urine or biopsy cultures, are vital for diagnosis.

Disseminated nocardiosis with Nocardia brasiliensis bacteremia in a patient with rheumatoid arthritis using tocilizumab.

Here, we present a case of disseminated nocardiosis, involving pneumonia, percutaneous abscess, and bacteremia, in a 67-year-old Japanese woman. She had also been treated for rheumatoid arthritis with prednisolone, methotrexate, and tocilizumab (interleukin-6 receptor inhibitor). Based on the 16S rRNA sequence analysis and a blast search, we identified the isolate as Nocardia brasiliensis. We discontinued methotrexate and tocilizumab on admission, and administered intravenous antimicrobial combination therapy for 6 weeks, followed by oral trimethoprim-sulfamethoxazole for 12 months, in total. Nocardia bacteremia is rare, often difficult to diagnose, and substantially fatal. However, due to our prompt diagnosis within one day of the onset of symptoms, and administration of appropriate treatment based on antimicrobial susceptibilities, this patient succeeded in surviving the infection. Not only microbiologists but also clinicians should be aware of the characteristic bacterial form of Gram/Kinyoun staining for early recognition of nocardiosis.