Peutz-Jeghers syndrome (PJS) is a rare, autosomal dominant condition characterised by mucocutaneous pigmented lesions, gastrointestinal polyposis and a significant risk of cancer. Laugier-Hunziker syndrome (LHS) is a benign condition with similar dermatological features, but with no systemic complications. STK 11 gene testing allows clinicians to differentiate between these two disorders. This case report compares the dermatological similarities in four individuals with PJS or LHS and illustrates the potential benefit of genetic testing. There is > 90% likelihood of identifying a mutation in STK 11 if a patient fulfils the diagnostic criteria for PJS. Lifelong risk management is advised for these individuals with confirmed PJS. Diagnostic confirmation is important to provide rational management, in particular, endoscopic cancer surveillance, and psychological support. STK 11 testing can confirm those at risk of PJS, who require lifelong surveillance, and possibly release those with a simple dermatosis, such as LHS, from invasive and thus potentially harmful surveillance.

Incidental findings are inevitable as clinical research and practice transitions from a single gene approach to a genomic approach. A novel deletion of the Fumarate Hydratase (FH) gene was identified in a 22 year old male who underwent a molecular karyotype as part of an autism spectrum disorder research project. This unexpected result implies a predisposition to Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC), a rare, autosomal dominant condition and has unforeseen implications for him and his family. We review the typical features and management of HLRCC and discuss the challenges that face health professionals, as genetic testing advances and becomes more accessible.