This deletion was noted in five of the 13 families, showing a high frequency, and was also shown to affect two genes that were located upstream of the STK11 gene, SBNO2 and GPX4, which are considered to modify STK11. This finding suggests that an abnormality in the genes that modify STK11 function may promote the development of PJS, even in the absence of a mutation in STK11 itself. This evidence concerns the gene STK11 and Peutz-Jeghers syndrome.