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Journal of Crohn's and Colitis: 10 (10)


Laurence J. Egan, Ireland

Associate Editors

Shomron Ben-Horin, IsraelSilvio Danese, ItalyPeter Lakatos, HungaryMiles Parkes, UKJesús Rivera-Nieves, USABritta Siegmund, GermanyGijs van den Brink, NLSéverine Vermeire, Belgium


Published on behalf of

Cap polyposis mistaken for Crohn's disease: Case report and review of literature

Geogry P. Kini, Iain Murray, Joanna Champion-Young, Michael Lau, Venkateswara Katta, Magnus Thorn, Michael P. Schultz
DOI: http://dx.doi.org/10.1016/j.crohns.2012.06.005 e108-e111 First published online: 1 April 2013


We report the case of a 19-year old male who presented with collapse and hypoglycemia associated with two weeks of frequent hard stools, abdominal pain relieved by defecation, postprandial vomiting and significant weight loss. Radiologically and endoscopically a diagnosis of Crohn's colitis was made and the patient was treated with steroids and immunosuppression. Following several hospital admissions treatment had to be escalated to include anti-TNF-α agents. Despite maximum therapy the patient continued to deteriorate symptomatically and biochemically with severe hypoalbuminemia and persistent anemia and a total colectomy was performed. Intra-operative finding was that of an inflamed large intestine and pseudo-polyposis but histology was reported as cap polyposis. The specimen was compared with the biopsies obtained from the earlier colonoscopies and it was felt that the previous samples were taken from areas of severely inflamed polypoid mucosa with histology mimicking colitis in inflammatory bowel disease.

  • Cap polyposis
  • Protein losing enteropathy
  • Hypoalbuminemia
  • Crohn's disease

1 Introduction

Cap polyposis is a very rare intestinal disease of unknown etiology which variably affects both sexes in their mid-fifties. Symptomatically however there can be significant overlap with Inflammatory Bowel Disease (IBD) such as Crohn's disease (CD) and ulcerative colitis (UC). These disorders are much more common, especially in New Zealand1 and typically affect young patients and those with a family history of IBD. Cap polyposis can easily be misdiagnosed as IBD as illustrated in our case.

2 Case

We report the case of a 19-year old Caucasian male who presented acutely with loss of consciousness and hypoglycemia of 2.3 mmol/L associated with two weeks of frequent hard stools containing fresh blood, abdominal pain relieved by defecation, post-prandial vomiting and weight loss of 10 kg. He had no significant past medical history, no recent travel history or infectious contacts and no non-steroidal anti-inflammatory drugs or illicit drug use. His maternal grandfather was diagnosed with colorectal cancer aged 62 years and a maternal cousin diagnosed with Crohn's disease aged 6 years. Physical examination found no abnormality aside from a tachycardia of 110–120 beats/min and some tenderness over the lower abdomen with no signs of peritonism. Blood test results at initial presentation are shown in Table 1 . Stool samples were negative for Clostridium difficile toxin and other pathogens. Abdominal X-ray was normal but a CT scan showed diffuse circumferential wall thickening involving the distal ileum and the entire colon with widespread mesenteric vascular congestion associated with multiple prominent lymph nodes. Proctosigmoidoscopy was normal macroscopically. Based on these findings a diagnosis of Crohn's disease was considered and treatment with steroids initiated. The patient represented two weeks later with a further episode of loss of consciousness and hypoglycemia of 1.9 mmol/L. Blood tests showed a further increase in C-reactive protein (83 mg/L), mild leukocytosis (11.1 × 106) and a further drop in serum albumin (24 g/L). Ileocolonoscopy was performed which showed multiple discrete ulcers of variable sizes, cobblestoning and thickened bowel wall involving the entire colon with rectal sparing (Fig. 1). Examination of the biopsy series (terminal ileum to rectum) showed changes throughout the entire colon consistent with chronic active pancolitis with sparing of the terminal ileum (Figs. 2, 3 ).

Figure 1

Markedly inflamed colonic mucosa with cobblestoning and fibrinopurulent exudates overlying multiple polyps.

Figure 2

Crypt branching and shortening.

Figure 3

Crypt abscesses with a mixed inflammatory infiltrate in the lamina propria.

View this table:
Table 1

Laboratory results on initial presentation.

Full blood countHemoglobin 130 g/L (NR 120–145), platelet 368 × 106 (NR 150–450), white cell 11.1 × 106 (NR 3–10)
Electrolytes and renal functionSodium 135 mmol/L (NR 135–145), potassium 3.9 mmol/L (NR 3.5–5.3), urea 3 mmol/L (NR 2.5–7), creatinine 79 μmol/L (NR 40–100)
Liver function testBilirubin 11 μmol/L (NR 2–21), ALP 73 U/L (NR 35–115), GGT 16 U/L (NR < 61), ALT 9 U/L (NR 8–41), total protein 67 g/L (NR 60–80), albumin 33 g/L (NR 35–50), globulin 34 g/L (NR 18–36)
Iron studiesSerum iron 3 μmol/L (NR 10–30), ferritin 68 μg/L (NR 20–350), transferrin 1.5, transferrin saturation 8% (NR 16–50)
C-reactive protein44 mg/L (NR < 3)
Stool specimenNegative culture for pathogens and Clostridium difficile toxin

In the following ten months the patient showed only partial clinical and biochemical improvement with less frequent bowel motions and improved appetite with some weight gain but developed pain in the large peripheral joints. However, he remained anemic (lowest hemoglobin 70 g/L) and hypoalbuminemic (lowest albumin 16 g/L), felt generally tired and fatigued, had pedal edema secondary to hypoalbuminemia but clinically no ascites. Symptomatically, he was treated with a blood transfusion, intravenous iron and a high protein diet. Adalimumab was commenced concurrent with prednisone but symptoms relapsed when the prednisone dose was tailed off. Treatment was switched to infliximab and azathioprine which resulted only in modest clinical and biochemical improvement. For further staging a wireless capsule endoscopy was performed which showed patchy erythematous areas in the proximal jejunum and multiple small polyps in the mid- and distal ileum. Gastroscopy and duodenal biopsies were unremarkable with no evidence of Helicobacter pylori infection. Finally, the patient was re-admitted with continuous weight loss and frequent small, hard bowel motions associated with persistent anemia, raised inflammatory markers and worsening hypoalbuminemia (20 g/L). Limited colonoscopy up to the sigmoid showed multiple pseudo-polyps, some grossly inflamed with the mucosa completely ulcerated/denuded. In agreement with the patient and in view of the progressive deterioration and failed medical management a total colectomy was undertaken. Macroscopically, a markedly inflamed colon was seen, showing large numbers of what appeared as mucosal pseudo-polyps measuring up to 10 mm in size with edematous mucosa in between. Histological examination showed multiple polyps, some with granulation tissue “caps”. The polyps showed no hamartomatous or adenomatous features and no evidence of malignancy (Figs. 4, 5). The specimen was compared with biopsies obtained from earlier colonoscopies and it was felt that the previous samples were taken from areas of severely inflamed polypoid mucosa with histology mimicking colitis as seen in IBD. Overall, the histological features in conjunction with the clinical presentation of a protein-losing enteropathy are consistent with that of cap polyposis.

Figure 4

Several polyps without the architectural features of hyperplastic polyps, adenomatous polyps or hamartomatous polyps.

Figure 5

Granulation tissue “caps” seen on some polyps.

3 Discussion

Cap polyposis is a rare and benign intestinal disease first described by Williams et al. in 1985 in a series of 15 patients who have no known family history of colorectal diseases.2 In 2004, Ng and associates reported the second largest case series of 11 patients with cap polyposis. This disease affects both sexes variably and any age groups with a median age of 52 years (range 12–76 years). A misdiagnosis of pseudopolyposis consistent with ulcerative colitis or Crohn's colitis has been reported. The exact etiology of inflammatory polyps in cap polyposis remains unknown. One theory attributes these polyps to abnormal colonic motility and repeated trauma to the colonic mucosa from chronic straining during defecation.3,5 Our patient reported hard small bowel motions indicating constipation. Similar histologic features are present in conditions referred to as “prolapse mucosal syndrome” such as prolapsing mucosa, solitary rectal ulcer syndrome, inflammatory cloacogenic polyps and gastric antral vascular atresia. Common symptoms include mucous diarrhea resulting in severe hypoalbuminemia, tenesmus but also chronic constipation with habitual straining and rectal bleeding.3,4 Typical endoscopic findings are multiple red, sessile or semi-pedunculated polyps, ranging from 1 to over 100 and in size ranging from a few millimeters to 2 cm, located at the apices of the mucosal folds with normal intervening mucosa.3,5 Often they are covered with a thick layer of fibrinopurulent exudate which appears like a “cap” as shown in Fig. 1 from our patient. The rectum and rectosigmoid colon are most commonly affected which is in contrast to our patient where the rectum was spared but the disease may extend to the cecum. Appearance on histology consists of elongated, distended, tortuous and hyperplastic crypts that become attenuated toward the mucosal surface with large number of inflammatory infiltrates in the lamina propria.3 The clinical course of this condition ranges from spontaneous remission to surgical resection of lesions but little is known about the long-term follow-up.6 Various medical treatments have been recommended including metronidazole, immunosuppressive agents and H. pylori eradication with variable response.3,5 Indeed several reports have been published indicating the beneficial role of H. pylori eradication in the treatment of cap polyposis.7,8 As our patient was tested negative for H. pylori, this treatment option was not available to us. The role of metronidazole in treating cap polyposis may be attributed to its anti-inflammatory effect rather than its antibiotic action.911 The use of the anti-TNF-α agent infliximab has been described in case reports with mixed results. Kim et al. reported the case of a 58-year old woman with cap polyposis who failed conservative treatment but showed clinical improvement seven days after a single dose of Infliximab (5 mg/kg) and at colonoscopy four weeks after the infusion the sessile polyps had decreased in size and numbers.12 The patient remained in remission clinically and endoscopically for the next three years. Bookman et al. reported the case of a 36 year old woman who had cap polyposis not responding to mesalamine, antibiotics and corticosteroids. The patient received four infusions of infliximab (5 mg/kg) at eight week intervals and showed clinical, endoscopic and histological resolution of the disease and this was maintained at 38 months after the last infusion.13 In contrast but consistent with our case, Maunoury et al. failed to show similar treatment benefit in their case of a 52-year old woman who had cap polyposis treated with rectosigmoid resection and disease recurrence after ten years who was given two infusions of infliximab (5 mg/kg) at four week intervals.14 Our patient did not respond to prolonged treatment with either adalimumab or infliximab and continued to have clinical, biochemical and endoscopic evidence of active disease. Complete polypectomy when possible may be curative in some patients while surgery is only reserved for those non-responsive to medical therapy but recurrence has been reported particularly with segmental colonic resection.3

At three months following total colectomy our patient remained in remission clinically and biochemically (serum albumin 40 g/L) and has gained weight.

Conflict of interest statement

This case report received no funding and there was no perceivable conflict of interest in its publication.


I would like to acknowledge the following co-authors: VK, IM, MT, JCY and MS contributed to the writing of the manuscript and reviewed the literature. ML reported the histology and contributed to the photographs.


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