Colon

• Focal active colitis (FAC) is a histologic term that denotes the presence of focal neutrophil infiltration within the colonic crypts or epithelium (Biomedicines 2023;11:2631)
• Nonspecific diagnosis that encompasses infectious (acute self limited) colitis and noninfectious active colitis

• Focal active colitis (FAC) is characterized by a single focus or multiple foci of neutrophilic infiltration of the crypts with an otherwise unremarkable colonic mucosa; the crypt architecture is well preserved with no evidence of chronic injury (Cureus 2020;12:e8140)
• FAC can be seen in the setting of acute self limited infectious colitis, evolving inflammatory bowel disease (IBD), ischemic colitis, Clostridium difficile colitis, drug induced or chemical injury, irritable bowel syndrome and bowel preparation artifact (Cureus 2020;12:e8140)
• Incidence of Crohn's disease (CD) in adults presenting with FAC is relatively low and varies between 0 and 13%, whereas the incidence of infectious type colitis has been demonstrated to be nearly 50% (Cureus 2020;12:e8140)
• In pediatric patients, a 24% rate of IBD is seen with FAC; however, when patients with associated terminal ileal inflammation were excluded, the rate dropped to 11% (similar to the rates of adults) (Hum Pathol 2018;74:164)
• FAC remains a diagnostic challenge; one must incorporate the patient's presenting history, medications and findings on endoscopy to help narrow the differential diagnosis

• Teenage girl with orbital myositis associated with focal active colitis (Childs Nerv Syst 2012;28:641)
• 82 year old woman presented with complaints of diarrhea, nausea, abdominal cramping, increased flatulence, anorexia and weight loss for the past 3 months (Cureus 2020;12:e8140)

Contributed by Safina Ahmed, M.B.B.S. and Saroona Haroon, M.B.B.S.

A 55 year old man presented with diarrhea, abdominal discomfort and flatulence. Colonoscopy shows patchy erythematous areas in the left colon. Endoscopic biopsy is taken and it shows the histology above. Which of the following statements is the most likely morphological diagnosis?

1. Focal active colitis
2. Lymphocytic colitis
3. Pseudomembranous colitis
4. Ulcerative colitis

A. Focal active colitis. Focal active colitis is the correct answer as there is focal cryptitis and crypt abscess formation. The crypt architecture is intact. Answer B is incorrect because there are no increased intraepithelial lymphocytes. Answer C is incorrect because pseudomembranous colitis typically has necroinflammatory exudate on the surface. Answer D is incorrect because crypt distortion is typically seen in ulcerative colitis of patients of this age range.

Comment Here

Reference: Focal active colitis

A 17 year old boy presented with bloody diarrhea and elevated fecal calprotectin. He had granulomata on upper GI biopsy and colonoscopic biopsy showed focal active colitis. Which of the following is the most likely underlying diagnosis?

1. Crohn's disease
2. Lymphocytic colitis
3. Pseudomembranous colitis
4. Ulcerative colitis

A. Crohn's disease is the correct answer because in the pediatric population, inflammatory bowel disease can just present by focal active colitis, even though the architecture is intact. Answer B is incorrect because lymphocytic colitis has increased intraepithelial lymphocytes. Answer C is incorrect because pseudomembranous colitis shows inflammatory exudate on the mucosal surface. Answer D is incorrect because ulcerative colitis doesn't show granulomas on upper GI biopsies.

Comment Here

Reference: Focal active colitis