Mycobacterium tuberculosis

 Hepatic TB seen in ∼ 1% of patients with active TB


image More common in HIV(+) patients





Etiology/Pathogenesis




• Transmission typically by inhalation
image Can reach liver by hematogenous spread or direct spread from GI tract


Clinical Issues




• Liver is usually involved as part of disseminated TB
• Most common symptoms overall are hepatomegaly, fever, abdominal pain, weight loss

• Tuberculoma/localized disease can mimic neoplasm and compress biliary tract, vessels

• Mortality ranges from 10-40%

image Worse prognosis with immune compromise, drug-resistant organisms


Microscopic




• Numerous granulomas ± central necrosis
image Coalescence of granulomas can produce tuberculoma

• Immunocompromised patients may have poorly developed granulomas or abscesses

• Acid-fast stains (+) in up to 60% of cases


Ancillary Tests




• Culture is more likely to be positive in cases with caseating necrosis
image May take weeks to grow

• PCR has 53-88% sensitivity and 96-100% specificity


Diagnostic Checklist




• Have high index of suspicion in patients with hepatomegaly, fever, respiratory symptoms, and elevated liver tests, especially if patient is from endemic area

image
Granuloma With Giant Cells
This liver biopsy in hepatic tuberculosis shows an expansile, portal-based granuloma with associated lymphocytes and giant cells. Note that the granuloma effaces the normal architecture of the liver.


image
Caseating Necrosis
This patient with disseminated tuberculosis had granulomas with central amorphous granular material, typical of caseating necrosis, within the liver and portal lymph nodes. Note the surrounding palisading histiocytes.

image
Miliary Tuberculosis in Liver
The liver from an autopsy of a patient with miliary tuberculosis shows a small granuloma with associated lymphocytes and multinucleated giant cells and very focal eosinophilic granular necrotic debris.

image
AFB Stain
Acid-fast stain shows a few acid-fast bacteria image with a slender, beaded appearance consistent with Mycobacterium tuberculosis.


TERMINOLOGY


Abbreviations




• Mycobacterium tuberculosis (MTB)

• Tuberculosis (TB)


Definitions




• Infection by  MTB
image ∼ 8.5 million people develop TB annually; extrapulmonary TB is increasing in frequency

– Hepatic TB seen in ∼ 1% of patients with active TB

– More common in HIV(+) patients


ETIOLOGY/PATHOGENESIS


Environmental Exposure




• Transmission typically by inhalation
image Can reach liver by hematogenous spread or direct spread from GI tract

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Apr 20, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Mycobacterium tuberculosis
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