Abdominal pain and bloody diarrhea in a 32-year-old woman
FURTHER WORKUP
2. What should be the next step in the work-up?
- CT enterography
- Skin biopsy
- Colonoscopy with biopsy
- C-reactive protein, erythrocyte sedimentation rate, and fecal calprotecting testing
The endoscopic appearance and histopathology of the affected tissues are crucial for the diagnosis. Differentiating between Crohn disease and Behçet disease can be particularly challenging because of significant overlap between the intestinal and extraintestinal manifestations of the two diseases, especially the oral lesions and arthralgias. Thus, both colonoscopy with biopsy of the intestinal lesions and biopsy of a cutaneous ulceration should be pursued.
No single test or feature is pathognomonic for Behçet disease. Although many diagnostic criteria have been established, those of the International Study Group (Table 2) are the most widely used.18 Their sensitivity for Behçet disease has been found to be 92%, and their specificity 97%.19
Both CT enterography and inflammatory markers would depict inflammation, but since this is present in both Crohn disease and Behçet disease, these tests would not be helpful in this situation.
Endoscopic appearance of Crohn disease and Behçet disease
Intestinal Behçet disease, like Crohn disease, is an inflammatory bowel disease occurring throughout the gastrointestinal tract (small and large bowel). Both are chronic diseases with a waxing and waning course and have similar extraintestinal manifestations. Typical endoscopic lesions are deep, sharply demarcated (“punched-out”), round ulcers. The intestinal Behçet disease and Crohn disease ulcer phenotype and distribution can look the same, and in both entities, rectal sparing and “skip lesions” have been described.20–22
Nevertheless, findings on endoscopy have been analyzed to try to differentiate between Crohn disease and Behçet disease.
In 2009, Lee et al23 published a simple and accurate strategy for distinguishing the two diseases endoscopically. The authors reviewed 250 patients (115 with Behçet disease, 135 with Crohn disease) with ulcers on colonoscopy and identified 5 endoscopic findings indicative of intestinal Behçet disease:
- Round ulcers
- Focal single or focal multiple distribution of ulcers
- Fewer than 6 ulcers
- Absence of a “cobblestone” appearance
- Absence of aphthous lesions.
The two most accurate factors were absence of a cobblestone appearance (sensitivity 100%) and round ulcer shape (specificity 97.5 %). When more than one factor was present, specificity increased but sensitivity decreased.
Using a classification and regression tree analysis, the investigators created an algorithm that endoscopically differentiates between Crohn disease and Behçet disease (Figure 1) with an accuracy of 92 %.23
Histopathologic analysis of both colonic and skin lesions can provide additional clues to the correct diagnosis. Vasculitis suggests Behçet disease, whereas granulomas suggest Crohn disease.
CASE CONTINUED: SKIN BIOPSY AND COLONOSCOPY
Punch biopsy of the skin was performed on the right anterior thigh. Histopathologic analysis revealed acanthotic epidermis, a discrete full-thickness necrotic ulcer with a neutrophilic base, granulation tissue, and vasculitic changes. There were no vasculitic changes or granulomas outside the ulcer base. Cytomegalovirus staining was negative. An interferon-gamma release assay for tuberculosis was negative. Eye examination results were normal.
Colonoscopy showed multiple deep, round, and confluent ulcers with a punched-out appearance and fissures with normal intervening mucosa in the entire examined colon (Figure 2). The terminal ileal mucosa was normal. Colonic biopsies were consistent with cryptitis and rare crypt abscesses. Vasculitis was not identified.
Although the histologic changes were nonspecific, at this point we considered Behçet disease to be more likely than Crohn disease, given the typical endoscopic appearance and skin changes.
