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Rare Case: Woman's Chimerism Revealed After Miscarriage

11/20/2025

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Summary

Story summary

A Brazilian woman miscarried and genetic testing showed a male karyotype (46,XY) in blood cells and a female karyotype (46,XX) in skin.
Doctors diagnosed her with chimerism from incorporating her twin brother's DNA during fetal development.
Dr. Gustavo Arantes Rosa Maciel described the case as the first known instance of complete blood chimerism in a woman, noting that after the miscarriage she later gave birth to a healthy boy.

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Story summary

A Brazilian woman miscarried and genetic testing showed a male karyotype (46,XY) in blood cells and a female karyotype (46,XX) in skin.
Doctors diagnosed her with chimerism from incorporating her twin brother's DNA during fetal development.
Dr. Gustavo Arantes Rosa Maciel described the case as the first known instance of complete blood chimerism in a woman, noting that after the miscarriage she later gave birth to a healthy boy.