c.4621C>T variant causing Gardner's syndrome in a Han Chinese family may be inherited through maternal mosaicism.

Gardner's syndrome is a rare autosomal dominant hereditary disease that is characterized by multiple colorectal polyps combined with extra-colonic presentation (such as osteoma or desmoid tumors) of familial adenomatous polyposis syndrome. Gardner's syndrome is caused by the mutation of the adenomatous polyposis coli () gene, which is located at 5q21. The aim of the current study was to investigate the gene mutations present in a Han Chinese family diagnosed with Gardner's syndrome. The 38-year-old proband presented with clinical symptoms, and was later diagnosed with Gardner's syndrome. Genomic DNA was extracted from the peripheral venous blood of 150 normal controls as well as the family members of the proband. Analysis of the respective gene sequences was performed using PCR amplification and Sanger sequencing. Pathogenesis associated with the mutation was investigated using reverse-transcription quantitative PCR and determined through bioinformatics approaches. Haplotype analysis was performed to identify the genetic source of the mutation(s). In the initial screening for variants, the c.4621C>T variant was detected in the proband and his son, but was not detected in the proband's affected mother. The mRNA expression changed significantly according to age and the presence of the mutation in the blood of the patients. Haplotype analysis suggested the presence of maternal mosaicism for this mutation. Haplotype analysis revealed that the c.4621C>T variant in a patient with Gardner's syndrome was most likely derived from his mother through mosaicism. These results indicate the necessity to verify the possibility of gonadal mosaicism when a proband diagnosed with Gardner's syndrome appears to exhibit a mutation.