Bloom Syndrome Presenting as Early-Onset Bilateral Breast Cancer and Multisystem Metabolic Disease: A Case Report.

Bloom syndrome is a rare autosomal recessive disorder caused by pathogenic variants in the BLM gene and is characterized by early-onset malignancy, growth deficiency, metabolic abnormalities, and cutaneous findings. We report the case of a 33-year-old woman with bilateral early-onset breast cancer, lipodystrophy, severe hypertriglyceridemia complicated by pancreatitis, and type 2 diabetes mellitus. Initial targeted genetic testing did not identify a causative variant. Comprehensive multigene testing subsequently revealed a homozygous likely pathogenic splice-site variant in BLM (c.98+1G>T), establishing the diagnosis of Bloom syndrome. This case expands the clinical and genetic spectrum of Bloom syndrome and illustrates that targeted cancer gene panels can fail to detect syndromic cancer predisposition disorders, leading to diagnostic delay. Expanded genetic testing should be considered early in patients with multiple primary malignancies accompanied by suggestive syndromic features, as timely diagnosis enables syndrome-adapted management, tumor surveillance, and family counseling.