【Objective】A full exome sequencing of an early-onset family Alzheimer′s disease (EOFAD) was conduct? ed to identify the mutational sites which may cause diseases. The result of the current study may provide suggestion to genetic counseling and prenatal diagnosis.【Methods】Whole exome sequencing was performed on the family members and software PolyPhen-2 as well as SIFT was employed for hazard prediction (Prediction on functional effects of the missense mutation).【Results】The heterozygous mutation c.758A>G (p.Tyr253Cys) in exon 9 of TTC3 gene had been identified in proband whose mother had been proved with heterozygous mutation c.758A>G. According to the family separation and related bioinformatics analysis

the mutant gene was a possible pathogenic mutation. 【Conclusion】 A new mutation was found of c.758A>G in TTC3 gene within a Chinese EOFAD family and a new mutation to the spectrum of genetic mutation in EOFAD was expanded. The finding provides a significant groundwork for future exploration on the mechanisms underlying EOFAD.