Fanconi anemia (FA) is a rare inherited disorder that impairs the body’s ability to repair damaged DNA, leading to bone marrow failure, physical abnormalities present at birth, and a significantly higher risk of cancer. Most people are diagnosed in childhood, and the condition affects roughly 1 in every 100,000 to 250,000 births worldwide. While historically severe, improvements in treatment have pushed the median survival age from about 20 years before the year 2000 to approximately 29 years today.
How Fanconi Anemia Affects DNA Repair
Your cells constantly sustain DNA damage, and healthy cells have a built-in repair system to fix it. One particularly dangerous type of damage is called an interstrand crosslink, where the two strands of a DNA molecule get chemically bonded together in a way that blocks the cell from reading or copying its genetic instructions. In people with FA, the repair pathway responsible for removing these crosslinks doesn’t work properly.
This pathway normally coordinates three separate repair strategies to untangle and fix the damage. When any of the genes that run this system carry mutations, crosslinks accumulate, cells die off or become unstable, and the risk of cancer rises. At least 22 different genes are now known to cause FA when mutated, each representing a different subtype of the disease.
Inheritance Patterns
The vast majority of FA cases follow autosomal recessive inheritance, meaning a child must receive a faulty copy of the same FA gene from both parents to develop the condition. Parents who each carry one faulty copy are typically healthy and unaware of their carrier status.
Two rare exceptions exist. One subtype is X-linked, meaning the mutated gene sits on the X chromosome. Boys who inherit the variant are affected, while girls who carry it on one X chromosome are usually not. The other exception involves a gene called RAD51, where FA follows an autosomal dominant pattern. In every reported case so far, the RAD51 mutation arose spontaneously in the child rather than being passed down from a parent.
Physical Signs at Birth
About 60% to 75% of children with FA are born with visible physical differences, though their type and severity vary widely. Skeletal abnormalities of the upper limbs, particularly the thumbs and forearm bones, appear in roughly 40% of cases. These can range from a slightly misshapen thumb to a completely absent thumb or forearm bone. Abnormal skin pigmentation, including light brown spots and areas of uneven coloring, also occurs in about 40% of affected individuals.
Other features can include short stature, small head size, kidney malformations, and differences in eye or ear structure. Some children with FA have no obvious physical abnormalities at all, which can delay diagnosis until blood counts begin to drop later in childhood.
Bone Marrow Failure
The hallmark complication of FA is progressive bone marrow failure, where the spongy tissue inside bones stops producing enough blood cells. This typically begins around age 7, though it can appear anytime from birth through the early 40s. Between 75% and 90% of people with FA develop bone marrow failure during their first decade of life.
The earliest sign is usually a drop in platelet counts, which leads to easy bruising and prolonged bleeding from minor cuts. As the marrow produces fewer red blood cells, fatigue and paleness set in. A decline in white blood cells follows, making infections more frequent and harder to fight off. For many families, falling blood counts are the first clue that prompts testing for FA.
Elevated Cancer Risk
People with FA face dramatically higher cancer rates than the general population, even beyond the blood cancers linked to bone marrow failure. By age 48, the cumulative incidence of developing a solid tumor reaches about 29%, and leukemia affects roughly 10%.
The cancers that are disproportionately elevated include head and neck cancers (especially of the mouth and throat), esophageal cancer, and vulvar cancer in women. These particular cancers occur at rates hundreds to thousands of times higher than expected. They also tend to appear at much younger ages than they would in the general population, sometimes in the teens or twenties.
Because of this risk, ongoing cancer screening is a critical part of managing FA. Current guidelines recommend dental and oral exams every six months starting at age 18 (or earlier if symptoms arise), annual skin exams, and gynecological exams for female patients starting with visual inspection of external genitalia at age 13 and comprehensive exams at age 18.
How It’s Diagnosed
The standard diagnostic test for FA is a chromosome breakage test. A blood sample is taken, and the white blood cells are exposed to chemicals that create DNA crosslinks. Cells from a person with FA are hypersensitive to this damage and show dramatically more chromosome breaks than normal cells. In one typical comparison, treated cells from an FA patient showed breaks in 95% of cells, compared to far lower rates in healthy samples.
Two chemicals are commonly used for this test, and both are equally effective at confirming the diagnosis. If the breakage test is positive, genetic testing identifies which specific gene is mutated, which helps determine the subtype and guides treatment decisions.
Stem Cell Transplant
The only treatment that can restore normal blood cell production is a hematopoietic stem cell transplant, sometimes called a bone marrow transplant. Healthy stem cells from a donor replace the faulty marrow, giving the body a new source of blood cells. Overall survival after transplant is approximately 83%, based on recent analyses spanning two decades of transplant data.
A matched sibling donor has traditionally been considered ideal, but outcomes with alternative donors, including unrelated matches from registries, have improved substantially. Recent data shows no statistically significant difference in survival rates between matched-sibling and alternative-donor transplants, which is encouraging for the many patients who lack a sibling match. Transplant does not, however, eliminate the elevated risk of solid tumors later in life, so cancer surveillance remains important even after a successful transplant.
Androgen Therapy
For patients who are not yet candidates for transplant or who lack a suitable donor, androgen therapy (a type of hormone treatment) can help stimulate blood cell production. About half of FA patients see meaningful improvement in their blood counts with this approach.
The tradeoff is a significant side-effect profile. Roughly 80% of treated patients develop elevated liver enzymes, a sign of liver stress that often requires dose adjustments. Masculinizing effects are universal: girls and women experience increased body hair and voice deepening, while boys and men may experience other hormonal effects. Long-term androgen use also carries risks of liver tumors and abnormal blood lipids. Androgen therapy is generally viewed as a bridge, buying time while other options are explored, rather than a permanent solution.
Life Expectancy and Long-Term Outlook
Data from the Italian FA registry, one of the largest and longest-running, shows cumulative survival of 91% at age 10, about 72% at age 20, and 47% at age 30. The median survival age of 29.1 years represents a meaningful gain over the pre-2000 era, when median survival sat around 20 years. These improvements reflect better transplant techniques, earlier diagnosis, and more structured cancer surveillance.
Living with FA means navigating a lifetime of monitoring: regular blood counts, cancer screenings, and attention to new symptoms. Many adults with FA live independently, attend school, and work, particularly those who have had successful transplants in childhood. The ongoing challenge is managing the long-term cancer risk that persists regardless of how well the blood disorder is controlled.