Solitary rectal ulcer transformation to cap polyposis in a 15-year-old child

BACKGROUND: Cap polyposis (CP) is a benign, non-malignant inflammatory disease that affects the rectum. It usually occurs during the 5th decade of life, but children could also be affected. Its specific pathology is unknown. Due to the clinical, endoscopic, and histologic similarities with other disorders such as inflammatory bowel disease, a thorough histologic evaluation is critical to avoid unnecessary interventions. This study presents a 15-year-old child with a previously reported case of solitary rectal ulcer (SRU) that developed into CP determined by colonoscopy and histologic findings. CASE PRESENTATION: A 15-year-old boy who was previously diagnosed with SRU presented to our office with rectal bleeding, mucoid discharge, and abdominal pain. Additional colonoscopy evaluation revealed multiple polyposes varying in size and shape limited to the rectum. Histologic examination revealed a characteristic cap of granulation tissue covering tortuous nondysplastic crypts in the inflamed stroma, indicating that SRU had transformed into CP. Based on the assessments, we planned to perform endoscopic mucosal resection of the lesions in multiple sessions. CONCLUSIONS: Despite the rarity of CP, the transformation from SRU may be one of its etiologies. Thus, thorough serial histologic evaluation is critical in children with rectal bleeding to avoid unnecessary or harmful interventions.