title: Total hip replacement infected with Mycobacterium tuberculosis complicated by Addison disease and psoas muscle abscess: a case report.
abstract: BACKGROUND
  Prosthetic joint infection due to Mycobacterium tuberculosis is occasionally encountered in clinical practice. To the best of our knowledge, this is the first report of a prosthetic joint infection due to Mycobacterium tuberculosis complicated by psoas abscesses and secondary Addison disease.
  
  
  METHODS
  A 67-year-old immunocompetent Caucasian woman underwent total left hip arthroplasty because of osteoarthritis. After 18 months, she underwent arthroplasty revision for a possible prosthetic infection. Periprosthetic tissue specimens for bacteria were negative, and empirical antibiotic therapy was unsuccessful. She was then admitted to our department because of complications arising 22 months after arthroplasty. A physical examination revealed a sinus tract overlying her left hip and skin and mucosal pigmentation. Her levels of C-reactive protein, basal cortisol, adrenocorticotropic hormone, and sodium were out of normal range. Results of the tuberculin skin test and QuantiFERON-TB Gold test were positive. Computed tomography revealed a periprosthetic abscess and the inclusion of the left psoas muscle. Results of microbiological tests were negative, but polymerase chain reaction of a specimen taken from the hip fistula was positive for Mycobacterium tuberculosis. Our patient's condition was diagnosed as prosthetic joint infection and muscle psoas abscess due to Mycobacterium tuberculosis and secondary Addison disease. She underwent standard treatment with rifampicin, ethambutol, isoniazid, and pyrazinamide associated with hydrocortisone and fludrocortisone. At 15 months from the beginning of therapy, she was in good clinical condition and free of symptoms.
  
  
  CONCLUSIONS
  Prosthetic joint infection with Mycobacterium tuberculosis is uncommon. A differential diagnosis of tuberculosis should be considered when dealing with prosthetic joint infection, especially when repeated smears and histology examination from infected joints are negative. Clinical outcomes of prosthetic joint infection by Mycobacterium tuberculosis are unpredictable, especially given the limited literature in this field and the uncertainty of whether medical treatment alone can eradicate the infection without prosthesis removal. Furthermore, this case report raises interesting issues such as the necessity of a follow-up evaluation after treatment based on clinical conditions, the utility of a more standardized length of treatment for periprosthetic tuberculous infection, and the importance of a high diffusion capacity of anti-mycobacterial agents in order to eradicate the infection.
authors.affiliation: Clinical Department, National Institute for Infectious Diseases 'L, Spallanzani', via Portuense 292, 00149 Rome, Italy. pasqualedenardo@libero.it.
authors.forename: Pasquale
authors.initials: P
authors.lastname: De Nardo
authors.forename: Angela
authors.initials: A
authors.lastname: Corpolongo
authors.forename: Aristide
authors.initials: A
authors.lastname: Conte
authors.forename: Elisa
authors.initials: E
authors.lastname: Gentilotti
authors.forename: Pasquale
authors.initials: P
authors.lastname: Narciso