Bloom syndrome is an autosomal recessive condition of genomic instability caused by increased sister-chromatid exchange, which results in a predisposition to a variety of cancers at a young age. The early ages of these cancers, as well as the nature of Bloom syndrome itself, alter the expected response to and toxicities of chemotherapy in patients with this condition. We report a 16-year-old patient with undiagnosed Bloom syndrome who presented with metastatic mucinous adenocarcinoma and tolerated palliative chemotherapy, initially with modified FOLFOX and subsequently with FOLFIRI, both at 50% dose reduction, without significant toxicity.