The detection rate of pathogenic STK11 variants in patients with a clinical diagnosis of PJS is high (up to 100%), using techniques that detect single nucleotide changes as well as larger deletions and duplications in the STK11 gene. Currently, there is no evidence for genetic heterogeneity in patients fulfilling the diagnostic clinical criteria for PJS without a germline STK11 PV. Thus pathogenic variants that cannot be identified by up-to-date methods in routine diagnostics should be considered in these cases. Level of evidence: moderate Strength of recommendation: strong