How Is Fanconi Anemia Diagnosed?
People who have Fanconi anemia (FA) are born with
the disease. They may or may not show signs or symptoms of it at birth. For
this reason, FA isn't always diagnosed when a person is born. In fact, most
people with the disease are diagnosed between the ages of 2 and 15 years.
The tests used to diagnose FA depend on a person's
age and symptoms. In all cases, medical history and family history are an
important part of diagnosing FA. However, because FA has many of the same signs
and symptoms as other diseases, only genetic testing can confirm its diagnosis.
Specialists Involved
A geneticist is a doctor or scientist who studies
how genes work and how diseases and different traits are passed from parents to
children through their genes. Geneticists do genetic testing for FA and can
provide counseling about how FA is inherited and the types of prenatal (before
birth) testing used to diagnose it.
An obstetrician may detect birth defects linked to
FA before your child is born. After your child is born, a pediatrician also can
help determine whether your child has FA.
A hematologist—an expert in diagnosing and
treating blood conditions—also may help diagnose FA.
Family and Medical History
FA is an inherited disease. Some parents are aware
that their family has a medical history of FA, even if they don't have the
disease. Other parents, especially if they're carriers, may not be aware that
there is any history of FA in their families. Many parents may not know that FA
can be passed from parents to children.
Information on your family's medical history is very
important to help your doctor diagnose whether you or your child has FA or
another type of condition with similar symptoms.
If your doctor suspects that you, your siblings, or
your children have FA, he or she may ask you detailed questions about any
personal or family history of
anemia,
surgeries related to your digestive system, or diseases of the immune system.
Your doctor also may ask you about your appetite, eating habits, and the
medicines you take.
If you know your family has a history of FA, or if
your answers to your doctor 's questions suggest a possible diagnosis of FA,
your doctor will order further testing.
Diagnostic Tests and Procedures
The signs and symptoms for FA aren't unique to the
disease. They're also linked to many other diseases and conditions, such as
aplastic anemia. For this reason, genetic testing is needed to confirm a
diagnosis of FA. Genetic tests for FA include the following.
Chromosome Breakage Test
This is the most common test for FA. It's available
only in special laboratories. It shows whether your chromosomes (long chains of
genes) break more easily than normal.
Sometimes, skin cells are used for the test, but
usually a small amount of blood is taken from a vein in your arm with a needle.
A technician combines some of the blood cells that were taken out with certain
chemicals. If you have FA, the chromosomes in your blood sample break and
rearrange when mixed with the test chemicals. This doesn't happen in the cells
of people who don't have FA.
Cytometric Flow Analysis
Cytometric flow analysis, or CFA, is done in a
laboratory to see how chemicals affect your chromosomes as your cells grow and
divide. Skin cells are used for this test. A technician mixes the skin cells
with chemicals that can cause the chromosomes in those cells to act abnormally.
If you have FA, your cells are much more sensitive to these chemicals. The
chromosomes in your skin cells will break at a high rate as they go through the
cycle in this test. This doesn't happen in the cells of people who don't have
FA.
Mutation Screening
A mutation is an abnormality in a gene or genes.
Geneticists and other specialists can examine genes in your cells, usually from
a sample of your skin cells. With special equipment and laboratory processes,
they can look for mutations in your genes that are linked to FA.
Diagnosing Different Age Groups
Before Birth (Prenatal)
If your family has a history of FA and you become
pregnant, your doctor may want to test you or the fetus for FA before birth.
Two tests can be used to diagnose FA in a developing fetus. They're done in a
doctor's office or hospital.
- Amniocentesis. This test is done 15 to 18 weeks
after a pregnant woman's last period. A doctor uses a needle to remove a small
amount of fluid from the sac around the fetus. A technician tests chromosomes
(chains of genes) from the fluid sample to see whether they have defective
genes linked to FA.
- Chorionic villous sampling (CVS). This test is
done 10 to 12 weeks after a pregnant woman's last period. A doctor inserts a
thin tube through the vagina and cervix to the placenta (the temporary organ
that connects the mother to the fetus). He or she removes a tissue sample from
the placenta using gentle suction. The tissue sample is sent to a lab to be
tested for genetic defects linked to FA. This test doesn't require anesthesia.
At Birth
Three out of 4 people who inherit FA are born with
birth defects. If your baby is born with certain birth defects, your doctor may
recommend genetic testing to confirm a diagnosis of FA.
Birth defects often linked to FA include:
- Missing, oddly shaped, or three or more thumbs
- Poorly developed or missing bones in the arms
- Hips, legs, hands, and toes that aren't fully or
normally formed
- Curved spine
- Eyes, eyelids, and ears that aren't fully or
normally shaped
- Skin discoloration
- Missing or misshapen kidneys
-
Congenital heart defects
- Mental retardation
- Serious problems with the digestive system
Childhood and Later
You or your child may be born with FA, but not have
birth defects. You may not be diagnosed with the disease until signs of bone
marrow failure or cancer begin to show. This normally happens within the first
10 years of life.
Signs of bone marrow failure begin to show most
often between the ages of 3 and 12, with 7 to 8 years as the most common ages.
However, 10 percent of children with FA aren't diagnosed until after the age of
16.
If your bone marrow is failing, you may show signs
of aplastic anemia. In aplastic anemia, your bone marrow slows down or stops
producing all three types of blood cells: red and white blood cells and
platelets. Aplastic anemia can be acquired after birth through exposure to
chemicals, radiation, or medicines; or, it can be inherited, as with FA.
Doctors diagnose aplastic anemia using:
- A physical exam and family and medical history.
- A complete blood count (CBC) to check the number,
size, and condition of your red blood cells. The CBC also checks the number of
white blood cells and platelets.
- A reticulocyte count, which counts the number of
new red blood cells in your blood to see whether your bone marrow is producing
red blood cells at the proper rate.
- A bone marrow aspiration, in which a small amount
of liquid bone marrow is removed and tested to see whether it's making enough
blood cells.
- A bone marrow biopsy, in which a small amount of
bone marrow tissue is removed and tested to see whether it's making enough
blood cells.
For more information, see the Diseases and
Conditions Index article on
Aplastic
Anemia.
If you or your child is diagnosed with aplastic
anemia, your doctor will have to determine the cause. If your doctor suspects
you have FA, he or she may order genetic testing. |