Histopathology and PCR based diagnosis in differentiating Intestinal Tuberculosis (ITB) and Crohn’s disease (CD) : A Review of Case Reports

The differential diagnosis of Intestinal Tuberculosis and Crohn’s disease remains a significant challenge as they present with similar clinical and histopathological manifestations. Since misdiagnosis is quite common in such instances, it is of utmost  importance to formulate a proper diagnosis and treatment plan.

While many studies have been performed, a major one conducted at Inha University hospital, Incheon, South Korea weighed the importance of histopathological features and PCR based detection of Mycobacterium Tuberculosis in distinguishing ITB from CD.

In this study, out of 334 selected cases, only 97 patients were confidently established with their final diagnosis ( 55 confirmed ITB and 42 confirmed CD cases ).Then their old biopsy slides were reviewed, applying 8 strict histopathological diagnostic parameters suggesting the involvement of Mycobacterium Tuberculosis. These parameters included:

1. Granuloma size- Large granulomas (>400 micrometers) were more suggestive of                                                          tuberculosis.

2. Number of granulomas- Multiple granulomas within a biopsy favoured the diagnosis of ITB.

3. Langhans Giant cells- The presence of multinucleated giant cells is highly associated with granulomatous TB.

4. Caseation necrosis- a feature highly characteristic of TB.

5. Confluent granulomas- formed when adjacent granulomas merged and lost their boundaries.

6. Discrete granulomas

7. Ulcers- Ulcers lined by continuous bands of epithelioid histiocytes, a feature associated with TB.

8. Perigranulomatous Lymphoid cuffs- refers to the presence of dense lymphoid aggregates around the granulomas.

With regards to these parameters, patients were divided into 4 histopathological groups to determine whether increasing TB associated microscopic features improved diagnostic accuracy. To complement these findings, three different PCR methods were used (In- House PCR, KIT A & B ), targeting two genetic markers- IS6110 & MPB64.

This study highlighted the importance of combining histopathological examination and Molecular diagnostic techniques ( PCR ) alongside clinical manifestations in order to obtain the most accurate diagnosis and necessary treatment. 

In other research studies conducted elsewhere, showed increase in Fecal Zonulin in the stool of patients with TB and CD. Even a particular study conducted on an elderly patient ,revealed endoscopic features similar to CD whereas the biopsy obtained later revealed the presence of Mycobacterium Tuberculosis. Another case report revealed the presence of TB in omental biopsy even though IGRA was tested negative.

These case studies further reinforce the importance of using combined diagnostic techniques and the need to avoid the harmful consequences from inappropriate treatment.