SHH medulloblastoma and very early onset of bowel polyps in a child with hamartoma tumor syndrome.

Phosphatase and tensin homolog () hamartoma tumor syndrome (PHTS) is a cancer predisposition syndrome characterized by an increased risk of developing benign and malignant tumors, caused by germline pathogenic variants of the tumour suppressor gene. gene variants often present in childhood with macrocephaly, developmental delay, and/or autism spectrum disorder while tumors and intestinal polyps are commonly detected in adults. PHTS is rarely associated with childhood brain tumors with only two reported cases of medulloblastoma (MB). We report the exceptional case of an infant carrying a germline and somatic pathogenic variant of and a germline and somatic pathogenic variant of who developed a MB SHH in addition to intestinal polyposis.