Evolution of filiform polyposis from classical pseudopolyposis in a pediatric ulcerative colitis patient

Abstract

Filiform polyposis (FP) is a morphologic variant of pseudopolyposis associated with inflammatory conditions of the gastrointestinal tract, namely, inflammatory bowel disease. Pediatric cases are uncommon in the literature. Here, we present a pediatric patient with FP arising from ulcerative colitis (UC). He initially presented at 7 years of age for an acute UC flare and was found to have classical pseudopolyposis. A follow‐up colonoscopy at age 9 showed the evolution of classical pseudopolyposis to FP. The patient clinically improved with sulfasalazine monotherapy and remained in remission based on consistent pediatric ulcerative colitis activity index scores of zero and normal‐range inflammatory markers. Repeat surveillance colonoscopy at age 14 showed persistent and diffuse FP in the background of healthy colonic mucosa. This case documents the development of FP from classical pseudopolyps in the setting of an asymptomatic patient in clinical remission.

1. INTRODUCTION

Pseudopolyps are found in up to 20% of patients with inflammatory bowel disease (IBD). ¹ These polyps are inflammatory byproducts formed from cycles of mucosal ulceration, regeneration, and remission. Histologically, these polyps consist of submucosal dilated lymphovascular cores with variably inflamed mucosa. ² Filiform polyposis (FP) is a rare variant of pseudopolyposis characterized by long vermiform, projections. ³ A recent review estimated that of the reported cases of FP, 46% occurred with UC, 37% with Crohn's, and 17% with other inflammatory conditions. ⁴ To our knowledge, few pediatric reports exist that describe FP or its natural history. Here we report the evolution of FP in a pediatric patient with ulcerative colitis (UC) with a previous history of classical pseudopolyposis.

2. CASE

A 7‐year‐old boy with ulcerative pancolitis was presented to our emergency department for abdominal pain and bloody stools concerning UC flare. He was reportedly diagnosed with UC at an outside institution 1 year prior but was not taking any medications at the time of this acute presentation due to noncompliance. His labs demonstrated anemia and positive fecal occult blood test, as well as hypoalbuminemia (2.2 g/dL), elevated C‐reactive protein (CRP: 11.00 mg/dL), and erythrocyte sedimentation rate (31 mm/h). Given unclear documentation pertaining to his initial diagnosis, he underwent restaging of his disease. Colonoscopy was notable for pancolitis (Mayo score 3) with rectal sparing, as well as numerous classical pseudopolyps throughout the ascending, transverse, and descending colon (Figure 1A). Histopathologic examination showed mildly active chronic colitis consistent with UC (cryptitis, crypt distortion, basal lymphoplasmacytosis). He received intravenous corticosteroids with clinical improvement and subsequently transitioned to oral prednisone. He was discharged after a 2‐week admission with azathioprine (1.15 mg/kg) and prednisone taper. At his first follow‐up visit 2 weeks later, his labs had improved, and his pediatric ulcerative colitis activity index (PUCAI) score was 0. In addition to an azathioprine dose increase (2 mg/kg), sulfasalazine with folic acid supplementation was also initiated.

Figure 1.

(A) Age 7, descending colon demonstrating classical pseudopolyps. (B) Age 9, descending colon showing interval development of filiform polyps. (C) Age 14, transverse colon showing persistence of filiform polyps, some of which are spanning the lumen. (D) Age 14, single filiform polyp found in the transverse colon, excised for pathology.

He was clinically doing well but was lost to follow‐up for 1 year. He returned to the clinic at age 9 and underwent a surveillance colonoscopy demonstrating the development of FP from the ascending to descending colon that was otherwise Mayo score 0 (Figure 1B). His azathioprine dosage was further increased (2.5 mg/kg) after subsequent testing showed 6‐thioguanine metabolite levels were subtherapeutic.

On follow‐up outpatient visits, he denied abdominal pain, diarrhea, or bloody stools (PUCAI 0). He was ultimately discontinued on azathioprine due to noncompliance and was continued with sulfasalazine monotherapy. CRP and erythrocyte sedimentation rate (ESR) remained within normal limits; however, over the following 2‐year period he was found to have persistently elevated fecal calprotectin levels (220–770 μg/g) while remaining clinically asymptomatic.

At age 14, repeat surveillance colonoscopy redemonstrated FP of similar character and distribution with a Mayo score 0 throughout the colon (Figure 1C,D) with evidence of ulcerative proctitis (Mayo score 3). The histology of one polyp demonstrated colonic epithelium with a central shared core of smooth muscle and dilated blood vessels characteristic of an FP (Figures 2 and 3). The mucosa adjacent to the polyp was histologically unremarkable without active (neutrophilic) inflammation or features of chronicity of damage (i.e., crypt distortion). Biopsies of the rectum, distant from the polyps, revealed mild active chronic colitis as seen previously.

Figure 2.

A low‐power magnification image of a polyp bisected along its long axis. The two pieces are the upper and lower fragments. The polyp surface is covered by colonic mucosa (+), and the internal core is comprised of lymphovascular structures (*). The left sides of the fragments have black ink on the cauterized surfaces. The right sides of the fragments are the tip surfaces.

Figure 3.

High‐power magnification of the same polyp. The mucosal surfaces (+) have a shared internal core of smooth muscle (sm), arterioles (art), venules (ve), and lymphatics (ly).

3. DISCUSSION

This present case adds to the small subset of pediatric reports of FP. ⁵ , ⁶ , ⁷ , ⁸ , ⁹ To our knowledge, all cases of FP in children were associated with IBD; however, FP has been reported in non‐IBD cases in adults. ¹⁰ As with classical pseudopolyps, FP generally develops following chronic colitis. An early retrospective cohort study found that the incidence of pseudopolyposis was associated with disease severity ¹ ; however, the relationship between the extent of polyp formation and disease severity has not been well studied. Why any given patient would develop classical or FP altogether remains unclear.

Previous reports on FP have documented polyp regression with medical therapy. ⁷ , ¹¹ Karaskova et al. report one pediatric case of inflammatory polyposis with UC that regressed with medical therapy. ⁷ In that case, the initial colonoscopy during an acute UC flare showed colitis and ulceration without polyposis. One year later, with the patient in remission on azathioprine maintenance alone, colonoscopy showed numerous pseudopolyps and filiform polyps. Medical therapy was not changed, and a subsequent colonoscopy the next year showed regression of the polyps.

In contrast, our patient was found to have diffuse pseudopolyposis during initial presentation to our institution, with subsequent morphologic features that evolved to a filiform appearance 2 years later. The progression of FP from pseudopolyposis has been reported anecdotally but is not well‐documented on endoscopy in the literature. ² Further, our patient's FP persisted for another 5 years and did not regress despite perceived clinical remission. This case is complicated by our patient's history of medication adherence issues. Since FP was first noted, his CRP and ESR were consistently normal. His most recent fecal calprotectin levels from 2 years prior were mildly elevated, though this may be accounted for by the patient's proctitis as seen on his most recent colonoscopy. Despite endoscopic and biochemical evidence of active inflammation in the rectum, the presence and persistence of diffuse filiform pseudopolyposis throughout the entire colon without background inflammation histologically makes this case stand out. Moreover, the patient remained effectively in clinical remission given consistent PUCAI scores of 0.

In conclusion, we present a pediatric UC patient with classical pseudopolyps that morphologically evolved to an FP subtype and persisted for years in the absence of diffuse chronic inflammation. This case shows that postinflammatory pseudopolyposis can persist despite normal clinical scores based on PUCAI, CRP, and colonic histologic remission. The long‐term significance of FP is unknown due to paucity of cases and longitudinal studies. Therefore, consistent follow‐up and surveillance, particularly in pediatric patients, will ultimately reveal the natural history of this unique pathology.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

Liaw V, Park J, Barth B, Santolaya J. Evolution of filiform polyposis from classical pseudopolyposis in a pediatric ulcerative colitis patient. JPGN Rep. 2024;5:79‐82. 10.1002/jpr3.12020