Fig. 1

a Endoscopic view of the larger polyp in the ileum. b Representative hematoxylin-eosin-stained tissue slices of the larger ileal polyp specimens confirms hamartomatous. Up, × 40 magnification; low, × 100 magnification. c Endoscopic view of the smaller polyp in the ileum. d The structure of STK11 gene. This novel mutation is within exon 1. e Schematics of the secondary structure or functional domains of the STK11 protein. The mutant protein results in a large-scale loss of kinase domain and a complete loss of the C-terminal domain compared to the wild type. NLS, Nuclear localization signal, NRD or CRD, N- or C-terminal regulatory domain. f Sanger sequencing forward and backward revealed a heterozygous deletion, c.243delG. g Evolutionary conservation of amino acid residues altered by c.243delG (p.K81Kfs*15) across different species. h Predicted by Swiss-Model online software, the mutant protein turns into an abnormal shape with loss of main functional domain compared with the wild type