04.09.2025 15:15
A woman named Ana Paula Martins was found to have both the XX chromosome associated with female sexual characteristics and the XY chromosome associated with males in her body. This case, which is seen for the first time in the medical world, astonished even the doctors. While the doctors believe that Paula's XY chromosomes were passed on to her from her twin brother while she was in the womb, they summarized the situation by saying, "So, a piece of her brother is circulating inside her."
Every cell in Ana Paula Martins' body contains XX chromosomes associated with female sexual characteristics. However, XY chromosomes belonging to a male were also detected in her blood cells. In this case, which is seen for the first time in the medical world, doctors believe that the XY chromosomes in Ana Paula's blood were passed from her twin brother while she was in her mother's womb. This discovery emerged during investigations following Ana Paula's miscarriage in 2022.
RESULTS SHOCKED DOCTORS The karyotype test conducted at the suggestion of the gynecologist showed that XY chromosomes were present in Ana Paula's blood. The results astonished both the doctors and Ana Paula. Gynecologist Gustavo Maciel, who works at Fleury Medicina e Saude and is a professor at the São Paulo University School of Medicine, stated, "I examined the patient. She had completely normal female characteristics. She had a uterus, ovaries, and her ovaries were active." Ana Paula was later referred to genetic specialist Dr. Caio Quaio at Albert Einstein Israel Hospital.
"SHE HAS HER BROTHER IN HER BLOOD" During the research, Ana Paula revealed that she has a twin brother. The DNA comparison showed that only the blood cells were identical to those of her twin brother. Prof. Maciel summarized the situation by saying, "The DNA in her mouth, the DNA in her skin is her own. But she has her brother in her blood." Dr. Quaio added, "So a piece of her brother circulates within her."
This is a "chimera" case where two different sets of DNA are found in one person's body. Typically, treatments like bone marrow transplants can lead to chimerism. However, according to Dr. Quaio, spontaneously occurring chimeras are extremely rare.
Researchers have noted that similar blood exchanges between siblings of different sexes in twin pregnancies have also been observed in mammals. It is believed that Ana Paula's placenta made contact with her twin brother in the womb, connecting blood vessels and allowing blood to pass from her brother to her.
Humans have 23 pairs of chromosomes, including sex chromosomes (XX or XY) "THE BLOOD VESSELS IN THE UMBILICAL CORD GOT TANGLED" Prof. Maciel stated, "A process called fetal-fetal transfusion occurred. At one point, the blood vessels in the umbilical cord got tangled, and all the blood samples passed to Ana Paula."
The blood cells of her brother settled in her bone marrow, starting to produce blood with XY chromosomes, while the rest of her body remained XX.
RARE SUCCESSFUL PREGNANCY Researchers believe this case could provide new insights into immunity and human reproduction. Ana Paula's immune system was able to tolerate her brother's cells without rejecting them. Prof. Maciel said, "Her case could contribute to a better understanding of organ transplantation."
Non-identical twins are usually as genetically different as other siblings. They share only about 50% of their DNA. SHE GAVE BIRTH TO A HEALTHY MALE CHILD While cases of women carrying XY chromosomes are generally associated with fertility issues, the situation was different for Ana Paula. During the research process, she became pregnant and gave birth to a healthy male child.
Genetic tests showed that the baby's DNA was normal: half of the chromosomes came from the mother, and half from the father; there was no genetic material from the uncle.
For Ana Paula, the most important thing was that this genetic condition did not affect her pregnancy. Paula said, "This was not something that could get in the way of my goal. My goal was to give birth to my baby."