Tuberculosis



Tuberculosis


Francisco G. Bravo, MD

Patricia J. Alvarez, MD










Two oral erosions with indurated white borders image on the buccal mucosa are indicative of periorificial TB.






Papules, plaques, and an ulcer are shown in a case due to perianal TB.


TERMINOLOGY


Abbreviations



  • Tuberculosis (TB)


Definitions



  • Cutaneous TB is chronic infectious disease caused by Mycobacterium tuberculosis, same bacteria that causes TB of lungs


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Mechanism of propagation is by direct inoculation, either through contiguous infection and hematogenous dissemination


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Rare disease



      • Represents 0.5-1.4% of all tuberculosis cases even in endemic countries such as India, China, South Africa, Peru, and Bolivia


Presentation



  • Multibacillary forms



    • Primary inoculation TB (tuberculous chancre)



      • Patients are healthcare workers or children with no BCG immunization exposed to M. tuberculosis through household member with pulmonary TB


      • Lesions are usually located on face, hands, and feet


      • Lesion is a papule or nodule that becomes ulcerated after 2 or 3 weeks of exposure


    • Scrofuloderma



      • Most common form of cutaneous TB in developing countries (patients have pulmonary or pleural TB)


      • Caused by contiguous propagation of bacteria from lymph node or bone


      • Most commonly affected areas are neck, axillae, thorax, and groin


      • Lesion is an abscess that becomes an ulcer surrounded by keloid tissue with underlying fistulae formation


    • Tuberculosis periorificialis



      • Oral TB is secondary to active TB, which affects the upper airway or lungs, and perineal TB is secondary to intestinal or genitourinary disease


      • Involved areas are buccal mucosa, around anus, vulva, or penis


      • Lesion is painful ulcer with pseudomembranous fibrinous base or occasionally a plaque similar to those seen in lupus vulgaris or TB verrucosa cutis


    • Acute miliary TB



      • Usually seen in patients with advanced pulmonary or disseminated TB


      • Trunk is most common location


      • Lesions are small macules or papules that become necrotic


    • Gumma



      • Secondary to hematogenous spread of bacteria that remain latent


      • Lesions are cold abscesses in extremities or on trunk


  • Paucibacillary forms



    • TB verrucosa cutis



      • Caused by reinoculation to M. tuberculosis in individual with previous exposure


      • Affects adults and children


      • Lesion is solitary, verrucose plaque on hands or feet


    • Lupus vulgaris



      • Most common form in India and Europe



      • Lesions due to hematogenous spread are found on face, and those located on extremities occur by reinoculation


      • Lesion is plaque with verrucous border and central atrophy; plaque is result of multiple coalescent papules and has classic apple-jelly appearance


    • Tuberculids: Erythema induratum of Bazin (EIB), lichen scrofulosorum, papulonecrotic tuberculid, lupus miliaris disseminatum faciei, and granulomatous mastitis



      • Erythema induratum of Bazin: Most common form of tuberculid; ulcerated subcutaneous nodules on posterior aspect of legs are classic


      • Papulonecrotic tuberculid: Lesions are found on extensor areas of extremities but can occur on lower abdomen, trunk, or buttocks; multiple symmetric papules with umbilicated, necrotic center


      • Lichen scrofulosorum: Occurs mostly in children as multiple miniature follicular or parafollicular lichenoid papules; almost always affects trunk


    • 2 controversial diseases; some consider both to be tuberculids



      • Granulomatous mastitis: Unilateral, ulcerated plaques or nodules on breast of female with positive contact of TB; has chronic course


      • Lupus miliaris disseminatus faciei: Multiple necrotic lesions on face, usually around eyelids, that leave varioliform scar


Laboratory Tests



  • Intradermal reaction to purified protein derivative (PPD) test or Mantoux test



    • > 5 mm in immunocompromised patients, HIV-positive patients, and patients with recent TB contact or x-ray changes consistent with healed TB


    • > 10 mm considered positive in adults and children from endemic areas or in setting of high risk (i.e., laboratory personnel involved with testing of TB)


    • > 15 mm considered positive in immunocompetent individuals with no known risk factor for TB infection


Treatment



  • Drugs



    • Standard therapy regiment



      • 2 months of quadruple therapy (isoniazid, rifampicin, pyrazinamide, and ethambutol)


      • Followed by 4 months of isoniazid plus rifampicin


    • Clinical response should be expected by week 4 or 6 of treatment


    • Some cases require longer than 6-month regiment


MICROSCOPIC PATHOLOGY


Histologic Features



  • 3 main patterns



    • Superficial tuberculoid granulomas with pseudoepitheliomatous hyperplasia (PEH), granulomas localized immediately below epidermis



      • Pattern seen in verrucous TB and lupus vulgaris of extremities


    • Deep tuberculoid granulomas that can show caseous necrosis localized in reticular dermis with normal, ulcerated, or acanthotic epidermis



      • Pattern seen in scrofuloderma


    • Superficial &/or deep tuberculoid granulomas with caseous necrosis (not always present); pseudoepitheliomatous hyperplasia is not present



      • Pattern seen in gummas, tuberculous chancre, TB periorificialis, facial lupus vulgaris, and lupus miliaris disseminatus faciei


  • Some important points



    • Scrofuloderma



      • Sometimes epidermis is normal and base of dermis is ceiling of granulomatous reaction


    • Lupus miliaris disseminatus faciei



      • Perifollicular granulomas as in rosacea can be seen


    • Erythema induratum of Bazin



      • Lobular panniculitis, necrosis of fat tissue, vasculitis of small or large vessels, and granulomatous formation


    • Papulonecrotic tuberculid and lichen scrofulosorum




      • Normal or ulcerated epidermis with superficial &/ or deep granulomas


ANCILLARY TESTS


PCR



  • Available and allows detection down to species level


Molecular Genetics



  • 16S rRNA gene sequence analysis



    • Currently very expensive, but another option for definitive identification down to species level

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Tuberculosis
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