A finding in genetic polymorphism analysis study: A case of non-mosaic 47, XXX without manifestations

•We report a rare case without clinical signs of Triple X syndrome, and born normal children.•We discussed the disturbing factors that could lead to misdiagnosis of nonmosaic trisomy X.•We discussed the interference exist in current forensic identification.•The pedigree study and the height ratio of alleles serve as interference in the deduction, and two X-STR kits and G-banding technology are applied to ascertain the final diagnosis of trisomy X.