<Table> <Tr> <Th_colspan="2"> Klinefelter syndrome </Th> </Tr> <Tr> <Th> Synonyms </Th> <Td> XXY syndrome, Klinefelter's syndrome, Klinefelter - Reifenstein - Albright syndrome </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> 47, XXY karyotype </Td> </Tr> <Tr> <Th> Pronunciation </Th> <Td> <Ul> <Li> / ˈklaɪnfɛltər / </Li> </Ul> </Td> </Tr> <Tr> <Th> Specialty </Th> <Td> Medical genetics </Td> </Tr> <Tr> <Th> Symptoms </Th> <Td> Often few </Td> </Tr> <Tr> <Th> Usual onset </Th> <Td> At birth </Td> </Tr> <Tr> <Th> Duration </Th> <Td> Long term </Td> </Tr> <Tr> <Th> Causes </Th> <Td> Two or more X chromosomes in males </Td> </Tr> <Tr> <Th> Risk factors </Th> <Td> Older mother </Td> </Tr> <Tr> <Th> Diagnostic method </Th> <Td> Genetic testing (karyotype) </Td> </Tr> <Tr> <Th> Treatment </Th> <Td> Physical therapy, speech and language therapy, counselling </Td> </Tr> <Tr> <Th> Prognosis </Th> <Td> Nearly normal life expectancy </Td> </Tr> <Tr> <Th> Frequency </Th> <Td> 1: 500 to 1: 1,000 males </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Klinefelter syndrome </Th> </Tr> <Tr> <Th> Synonyms </Th> <Td> XXY syndrome, Klinefelter's syndrome, Klinefelter - Reifenstein - Albright syndrome </Td> </Tr> <Tr> <Td_colspan="2"> 47, XXY karyotype </Td> </Tr>

Where does the extra x chromosome come from in klinefelter syndrome