Colon non tumor
Infectious colitis (specific microorganisms)
Mycobacteria infections other than TB

Author: Lili Lee, M.D. (see Authors page)

Revised: 9 January 2017, last major update February 2014

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Mycobacteria[title] colon
Cite this page: Mycobacteria infections other than TB. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colonMAI.html. Accessed October 18th, 2017.
Definition / general
  • Associated with HIV infection
  • Recommended to perform acid-fast stain on all mucosal biopsies in HIV+ patients
  • If present in gut, is usually disseminated, with positive stool and blood cultures
Terminology
  • Mycobacteria other than TB (MOTT)
  • Nontuberculous mycobacteria (NTM)
Epidemiology
  • Of the Mycobacteria other than TB (MOTT), Mycobacterium avium-intracellulare complex (MAC) is the most commonly isolated mycobacteria
  • Often associated with HIV infection, commonly infects immunocompromised and elderly patients
  • May be due to contaminated endoscope (Kekkaku 1995;70:629)
Sites
  • Ileocecal area is most commonly involved (90%) similar to Mycobacterium tuberculosis infection
Clinical features
  • Nonspecific symptoms of fever, night sweats, weight loss, fatigue, diarrhea, abdominal pain
Diagnosis
  • AFB smear, blood/sterile site culture, tissue biopsy
  • Multiplex PCR, DNA probes, DNA sequencing for specific NTM speciation
Laboratory
  • MAI complex:
    • No cording on Lowenstein-Jensen/Middlebrook broth
    • Nitro-α acetylamino β hydroxypropiophenone (NAP test) resistant (vs. Mycobacterium TB which is inhibited)
    • Para-nitrobenzoic acid (PNB test) resistant (J Lab Physicians 2010;2:89)
    • Non-chromogen
    • Slow grower (>7 days), and niacin inhibits growth
Radiology images

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Jejunal loops and extensive ymphadenopathy (MAI)

Case reports
Treatment
  • Two or more antimycobacterial drugs (clarithromycin, ethambutol, rifampin, etc.)
Clinical images

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Mimicking Whipple disease

Gross description
  • Diffuse mucosal fold thickening mimicking Whipple disease
Microscopic (histologic) description
  • Lamina propria expanded by a lymphohistiocytic infiltrate
  • Duodenal infection may resembles Whipple disease, but without fat vacuoles
Microscopic (histologic) images

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H&E and AFB



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Colonic crypt and masses of histiocytes

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Histiocytes in lamina propria (PAS)

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Intracytoplasmatic short acid fast bacilli (Ziehl-Neelsen)

Positive stains