Dear Editor: Lynch syndrome is an autosomal dominant inheritance and the most hereditary form of colorectal cancer [1]. The identification of the molecular genetic basis of Lynch syndrome enabled the implementation of predictive testing in families with a proven mutation. A prerequisite to detect patients with Lynch syndrome is the knowledge of the clinical and histopathological features of this disease [2]. The molecular genetics underlying mechanism is a mutation in one of the mismatch–repair genes (most commonly MLH1, MSH2, and MSH6), that has added significantly important information to the recognition of this disease and the search for high-risk individuals as well as offering them a genetic counseling. We report a rare mutation in gene MLH1 (1171 G>K) in nine members of a family, some of them with undetected Lynch syndrome. The genetic analysis were performed to confirm or to detect possible predisposition to hereditary nonpolyposis colorectal cancer (HNPCC). Six members of this family case present the single mutation in MLH1 117-1 G>K and some of them were confirmed by the doctor to be affected by Lynch syndrome. However, there are no other confirmed results of the pathogenicity effect of this mutation. There are many human online databases where the mutations in different syndromes could be included, such as www. ensembl.org, http://www.ncbi.nlm.nih.gov/gene, and www.hgmd.cf.ac.uk/. And even exclusive database for gastrointestinal hereditary tumors such as http://www.insightgroup.org/meetings/MMR/. However, none of them described or included the variants analyzed in the present case report. The case analysis started in a 59-year-old woman who had been diagnosed with HNPCC and fulfilled the Bethesda and Amsterdam Criteria. She was also confirmed by genetic analysis of mismatch repair (MMR) genes (MLH1, MSH2, and MSH6) by describing mutations in these genes such as 211+9 C>G in MSH2, 3,438+14 A>T in MSH6 and three others in MLH1 being one of them 117-1 G>K mutation. Due to the accelerated carcinogenesis of colorectal cancer (CRC) full colonoscopies are recommended but there are also others options such as the searching of germline mutation carriers. The discovery of mismatch repair germline mutations has improved the search for high-risk individuals throughout families who, with genetic counseling, may become candidates for germline mutation testing [1]. For these reasons, others members of this family (direct relatives and in different generations) has been analyzed in MMR genes, two more sisters 68 and 62 years old, both of them with only 117-1 G>K mutation and later clinically confirmed of Lynch syndrome. One of them, was also affected by endometrial cancer. They also had a death father of CRC and another sister affected by this syndrome. Their descendents were also studied in MMR genes with 28, 30, 31, and 40 years old, all without symptoms of Lynch syndrome but with a direct relative affected by CRC or endometrial cancer. After the genetic analysis, it was confirmed that all of them have 117-1 G>K mutation, but only this mutation. Others family members were also included to genetic analysis such as two cousins without previous symptoms of CRC, but one of them with endometrial cancer and a mother and a sister affected by this same cancer. All of them have the 117-1 G>K mutation. J. L. Martin Ruiz (*) Unidad Gestion Clinica Digestivo, Hospital Universitario S. Cecilio de Granada, Avenida de Madrid s/n Granada, Spain e-mail: jlmartin@ugr.es