Subsequently, mutations in genes of the mismatch repair (MMR) pathway, particularly MSH2, MLH1 and MSH6, the TGF-β signalling pathway genes, SMAD4 and BMPR1A, and the serine/threonine kinase gene STK11, were revealed as the causes of HNPCC [15,16,17,18,19,20,21,22,23,24,25,26], Juvenile Polyposis syndrome (JPS) [27,28] and Peutz-Jeghers syndrome (PJS) [29] respectively. The gene discussed is MLH1; the disease is Peutz-Jeghers syndrome.