Doctors stunned to see 'male blood' in Brazilian woman who suffered miscarriage

A woman in Brazil was shocked to learn that her blood carried male chromosomes, but this did not affect her appearance in any way. She learnt of this following a miscarriage at the age of 35. When doctors ran tests to understand what had happened, they were looking for a genetic clue in the blood. And Voila! they did find something extraordinary. The tissues showed two genetic lineages, pointing to chimerism, that is, when two sets of genes live in one body. Dr Gustavo Arantes Rosa Maciel, a genetics professor at the University of São Paulo, said that the woman lost her baby at seven weeks. The doctors went for chromosome testing to see whether an inherited trait could have caused it.

The blood test returned a result that is seen in males, leading the doctors to think that there could have been some technical error. So, they repeated the test. Gustavo met the patient and noted that she had "all the normal female characteristics. She had a uterus, ovaries… the ovaries were functioning normally." Her skin cells carried the usual female chromosomes, which led the medical team to look for a better explanation for the presence of male chromosomes.

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Her blood had XY set, while her skin had XX

A karyotype test that shows chromosome sets revealed that the woman's blood had 46, XY, while the skin cells taken from another part of her body had 46, XX. Typically, each human cell carries 23 pairs of chromosomes. To be fully sure, the blood test was repeated and compared with chromosome testing from skin cells. A physical check was also carried out, which showed the woman had basic female anatomy, hormone levels were within normal range, puberty was normal, with regular menstruation that began at 13. The doctors concluded that with nothing else to explain her condition, chimerism was the most likely explanation.

They classified her condition as "blood chimerism", and later learnt that she had a twin brother, and the genetic variants in her blood matched those in his blood. This caused different sets of genetic codes in her blood and other tissues.

The doctors revealed that the woman became pregnant once again 11 months later and was given progesterone to support early pregnancy. She faced no complications this time around and delivered a healthy baby boy. The baby was perfectly healthy and inherited equal number of genes from his father and mother.