Oldest case of a rare disco genetic disease

image: Photographs of the skull show front (A) and profile (B) views with probable malocclusion and maxillary prognathism denounced by atypical dental wear.
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Credit: The Lancet

A group of international researchers has uncovered evidence of an extremely rare genetic condition that gives men an extra X chromosome, reporting the oldest clinical case of Klinefelter syndrome to date.

The evidence comes from a 1,000-year-old skeleton from Portugal.

Klinefelter syndrome is a rare genetic disorder in which individuals are born with an extra copy of the X chromosome, occurring in approximately one in every 1,000 genetic male births.

The study coordinated by Dr. João Teixeira, ARC DECRA Fellow at the Australian National University (ANU), brought together a multidisciplinary team that combined genetic, statistical, archaeological and anthropological information to make a definitive diagnosis.

The team began by analyzing genetic information obtained from a skeleton found in northeastern Portugal that had been dated to the 11th century by researchers from the University of Coimbra in Portugal.

“We were immediately excited the first time we looked at the results,” Dr. Teixeira said. “However, ancient DNA is often degraded and low quality and abundant, which means we were initially cautious.”

The researchers say the findings will help set a historical record for Klinefelter syndrome, as well as improve understanding of its prevalence throughout human history.

“Our research shows the immense potential of combining different data sources to study the human past and the frequency of different health conditions over time,” said Dr Teixeira.

Associate Professor Bastien Llamas, Head of Molecular Anthropology at the Australian Center for Ancient DNA, said: “In recent years, ancient DNA has helped rewrite the history of human populations around the world. Our study demonstrates that it is now a valuable resource for biomedical research and the burgeoning field of evolutionary medicine.”

The DNA was extracted by a PhD student at the University of Adelaide, Xavier Roca-Rada, who said “genetic analysis was undertaken to computer map degraded DNA fragments from the X and Y chromosomes on the reference human genome”.

Given the state of preservation of the specimen, the researchers were also able to determine physical traits of the skeleton consistent with Klinefelter syndrome.

“Given the fragile state of DNA, we developed a new statistical method that could take into account the characteristics of ancient DNA and our observations to confirm the diagnosis,” said Dr Teixeira.

“Although the study offers compelling evidence for the genetic history of Klinefelter syndrome, no sociological implications can be drawn from this diagnosis.”

The researchers suggest that their new method of analyzing this particular skeleton could be further improved to study different chromosomal abnormalities in other archaeological specimens, including Down syndrome.

This research is published in The Lancet. An image is also available for download.


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