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Tuberculosis


Discussion

  • although the disease is generally more likely to be chronic, acute mycobacterial arthritis has been reported;
  • periarticular bone lesions may accompany the synovial involvement;
  • pulmonary tuberculosis is evident in only half the patients with skeletal involvement;
  • pulmonary TB signs vary with stage of dz, few early on;
    • later high fever, wt loss, prolonged, productive cough, anemia, high count of acid-fast in sputum;
  • note the high prevalence of HIV in tuberculosis patients and vice versa (5-10% of HIV patients will have TB);

tuberculous spondylitis

appendicular involvement

  • look for metaphyseal lytic lesions with little or no sclerosis, and no periosteal reaction;

juxta-articular / joint involvement

  • hips and knees are affected most frequently;
  • may present as gradually worsening arthritis but is often mistaken for some other form of arthritis (such as "mono-articular rheumatoid arthritis" or PVNS);
    • peri-articular osteopenia is common;
    • unlike most forms of arthritis, TB joint involvement is most often mono-articular;
    • note that in TB arthropathy, the joint space will often be maintained (unlike RA);

phalangeal tuberculous osteitis:

  • look for soft tissue swelling, cortical thinning, medullary destruction, and periosteal
    reaction involving the middle and distal phalanx;

diff dx

reference

Protection of Health Care Personel

  • historically transmission rate has been high;
    • in the past, when strict prevention measures were not manditory, there have been some reports of nearly half of health care
      students becoming PPD positive after 1 year;
    • patients known or suspected to be infected need to wear a HEPA mask and need to be placed in respiratory isolation;
      • respiratory isolation should include a room w/ special ventilation, optimally with HEPA filters;
    • elective surgery on actively infected patients should be delayed until the disease is treated and enters a latent phase;

Skin Testing

  • in the U.S. about 10-15% of the population will have positive test;
  • patients who have been given the bacille Calmette Guerin vaccine will have positive tests;
  • w/ infection, skin tests are usually, but not always, positive;
  • false negative tests will occur in malnourished patients and AIDS patients;
  • skin testing in a patient w/ an active infection may result in skin slough;

Laboratory Diagnosis

  • bacterium is a thin rod w/ rounded ends;
  • classic histologic pattern reveals central necrotic area surrounded by histiocytes and occasional giant cells with nuclei
    positioned at the margin of the cell;

Ziehl-Neelsen Staining Method

  • note potential false negative results are a frequent occurance;
  • tuberculum is acid fast (resist decolorization w/ acids)
  • diff dx: Myobacterium marinum

Culture

  • requires use of enriched medium and adequate oxygenation;
  • cultures visible at 2-4 weeks;
  • note that joint aspiration may not produce positive culture, and w/ suspected joint infection, a synovial biopsy may be required;

Medical Treatment of Tuberculosis Infection

preventive therapy

  • preventive therapy with insoniazid given for 6-12 months is effective in decreasing the risk of future tuberculosis;
  • persons for whom preventitive therapy is indicated include: household members and other close contacts of potentially
    infectious persons;
  • newly infected persons; persons with past tuberculosis or with a significant tuberculin reaction and abnormal chest films in whom current TB has been excluded;
  • infected persons in special clinical situations such as sillicosis, diabetes mellitus, adrenocorticosteroid therapy;
  • persons at high risk of developing severe forms of tuberculosis, if infected due to contact w/ a person having INH resistant
    organisms, should be treated with rifampin rather than INH;

acute infection

  • isoniazid, rifampin, and pyrazinamide (20-25 mg / kg / day) given for 2 months, after which time isoniazid and rifampin for 4 months is effective treatment in patients with fully susceptible organisms who comply with the treatment regimen;
    • 9 month regimen consisting of isoniazid and rifampin is also highly successful;
  • need for additional drug in initial phase is not certain unless isoniazid resistance is suspected;
    • w/ suspected INH resistance, consider the addition of ethambutol in initial phase;
  • children should be treated in essentially the same way as adults using appropriately adjusted doses of the drugs;

dormant infection

  • rifampin (10 mg/kg/day) and pyrazinamide are most effective

References