Bloom syndrome (BS) is an extremely rare autosomal recessive genetic disorder caused by a mutation in the BLM gene (1). The diagnosis of BS should be considered in patients with growth retardation of prenatal onset, a photosensitive rash in a butterfly distribution over the cheeks, and an increased risk of cancer at an early age. (2) Clinical manifestations also include short stature, dolichocephaly, prominent ears, micrognathia, malar hypoplasia, immunodeficiency, type II diabetes, hypogonadism associated with male infertility and female subfertility (3,4). The risk of malignancy in Bloom syndrome is 150–300 times greater than in the general population, with around 25% of patients developing cancer at a mean age of 20.7 years (5,6). In BS the risk of colon cancer is significant, affecting around 12% of patients, with a mean diagnosis age of 35.4 years (7)

In this case series, we describe seven related patients—siblings and cousins, both male and female—with genetically confirmed Bloom syndrome who underwent screening colonoscopy because of their high-risk status. All were asymptomatic, and their mean age was 24.7 years.

Colonoscopy revealed multiple polyps in each patient, several of which were safely removed using cold snare polypectomy. What was particularly striking, however, was that all seven patients had a large sessile rectal lesion, with an average size of 34 × 27 mm. These lesions were completely resected using endoscopic mucosal resection (EMR).

Histopathology showed that every rectal lesion was a mucinous adenoma with high-grade dysplasia. This is highly unusual, as mucinous adenomas are rare overall and even less common in the rectum. Finding this pattern repeatedly within one extended family highlights the unique behavior of colorectal neoplasia in Bloom syndrome.

At six-month follow-up, colonoscopy confirmed no residual lesions in any patient. Due to their increased lifetime risk of both early and advanced colorectal cancer, All seven patients have since continued on annual colonoscopy surveillance.

This case series demonstrates how asymptomatic patients with Bloom Syndrome may experience the early development of significant colorectal lesions. The finding of rectal mucinous adenomas with high-grade dysplasia emphasizes how crucial  routine screening colonoscopy is for this high-risk group. Early screening and timely endoscopic management remain essential cornerstones in preventing the progression of colorectal cancer.