Whole exome sequencing of Nepalese siblings with Factor X Deficiency identifies an ultra-rare F10 p.F71S mutation: The first homozygous report outside Algeria
This study presents the first molecular characterization of Factor X deficiency in Nepal, identifying an ultra-rare homozygous F10 p.F71S mutation in two siblings that marks the first global report of this variant outside the Algerian Kabyle population, thereby challenging existing ethno-geographic paradigms of mutation distribution.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Blood is a complex fluid that keeps our bodies running, but it also has a built-in repair system to stop bleeding when we get hurt. This system relies on a team of proteins, known as clotting factors, that work together like a chain reaction to form a scab. One of the most important members of this team is a protein called Factor X. When Factor X is missing or broken, the chain reaction stalls, and even a small cut can lead to dangerous, uncontrolled bleeding. This condition is known as Factor X deficiency, a rare genetic disorder that affects only a tiny fraction of the population. Because the symptoms can vary widely and the condition is so uncommon, doctors often struggle to pinpoint the exact cause in individual patients, leaving many without a clear diagnosis or the right treatment.
In a new study, researchers set out to solve this mystery for two siblings in Nepal who had been suffering from severe bleeding issues since childhood. The brother and sister, both from the Brahmin community, experienced frequent bruising, bleeding gums, and painful swelling in their joints. While they had received care for their symptoms, the specific genetic reason behind their illness remained unknown. To find the answer, the team turned to a powerful technology called whole exome sequencing. This method acts like a high-speed scanner for the parts of our DNA that contain the instructions for making proteins. By reading the genetic code of the two siblings, the researchers could compare their DNA against the rest of the human population to find the single, tiny error responsible for their condition.
The search led the scientists to a specific gene called F10, which holds the instructions for building Factor X. Inside this gene, the researchers discovered a unique change in the DNA sequence that was present in both siblings. This change swapped one building block of the protein for another, turning a stable, water-repelling part of the molecule into a water-attracting one. This small switch happened in a critical section of the protein known as the Gla domain, a region essential for the protein to latch onto cell surfaces and start the clotting process. Because both siblings inherited this exact same change from their parents, and because the change was predicted by computer models to break the protein's function, the team confirmed that this specific mutation was the cause of their disease.
What made this discovery truly remarkable was the history of this particular mutation. Before this study, the same genetic error had only ever been found in a specific group of people in Algeria, where it was so common that scientists believed it was a "founder effect," meaning it originated from a single ancestor in that community long ago. Finding this same mutation in a family from the Himalayas, thousands of miles away and with no known connection to the Algerian families, was a surprise. The researchers checked massive global databases of human genetics and found no other records of people with two copies of this mutation outside of Algeria. This suggests that the mutation either traveled across the world in the distant past, carried by ancestors who migrated, or that it happened to occur independently in two different places, a rare event known as a recurrent mutation.
To be absolutely certain of their findings, the team did not rely solely on the computer scan. They performed a second, more traditional test on the DNA of the siblings and their parents. This confirmed that the parents each carried one copy of the mutation without showing any symptoms, while the children inherited one copy from each parent, resulting in the disease. This pattern fits the classic rule for how rare bleeding disorders are passed down in families. The study also ruled out other possibilities, such as the idea that the siblings might have different genetic problems or that the mutation was a harmless variation found in healthy people. The evidence pointed clearly to this single genetic change as the culprit.
This work represents the first time Factor X deficiency has been genetically mapped in Nepal, filling a significant gap in our understanding of rare bleeding disorders in South Asia. By identifying the specific cause of the illness, the study provides a clear path forward for the family. It allows doctors to offer precise genetic counseling, helping the family understand the risks for future children and enabling them to make informed decisions about their health. Beyond this single family, the discovery expands the global map of human genetic diversity, showing that a mutation once thought to be confined to one corner of the world can appear in another, challenging our assumptions about how genetic diseases spread and evolve across the planet.
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