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Fanconi's anemia
Alternative
names
Anemia - Fanconi's;
FA
Definition
Fanconi's anemia is an inherited disease
that primarily affects the bone marrow, resulting
in decreased production of all types
of blood cells. The lack of white blood cells predisposes
the patient to infections, while the lack
of platelets and red blood cells may result in
bleeding, and fatigue (anemia), respectively.
It is also associated with a broad variety of
physical anomalies.
Fanconi's anemia is distinct from Fanconi's
syndrome, a rare kidney disorder in which nutrients
are lost through the urine.
Causes
and risks
Fanconi's anemia is inherited in an autosomal
recessive fashion, thus one copy of an
abnormal gene is passed on by each parent. It
occurs in all racial and ethnic groups. It is
classically diagnosed between 2 and 15
years of age.
The disease is caused by a genetic defect
that prevents cells from fixing damaged
DNA or removing toxic, oxygen-free radicals
that damage cells. Patients may be suspected
of having the disease, if they have particular
birth defects or develop decreased blood counts.
Prevention
Fanconi’s anemia is an inherited disorder,
and little can be done to prevent the disease
short of genetic counseling for families known
to be affected as a result. However, some complications,
such as pneumococcal pneumonia, hepatitis, and
varicella infections, can be prevented by vaccination.
Additionally, patients should avoid known carcinogens
and undergo regular cancer screening to detect
malignancies early in their course, should they
arise.
Symptoms
This set of physical abnormalities
occur in 80% of the cases:
Other potential symptoms:
-
Mental retardation
- Learning disability
- Low birth weight
- Failure to thrive
- An affected sibling
Signs
and tests
Common tests performed for evaluation of Fanconi's
anemia include:
- CBC (complete blood count) initially demonstrates
low platelets. (thrombocytopenia), then low
neutrophils (a type of white blood cell),
and finally low hemoglobin (anemia), which
develops over months to years.
- Bone marrow biopsy.
- Clastogenic stress-induced chromosomal breakage
analysis on blood cells of patients and
their siblings to diagnose the disease. Here,
chemotherapy is added to a blood sample to
check for abnormal damage to chromosomes.
- HLA tissue typing on the patient and their
family members to determine if any are matching
bone marrow donors.
- Hand X-ray, and other imaging studies (X-ray,
CT scan, MRI) to evaluate any anomalies.
- Hearing test.
- Developmental assessment.
- Ultrasound of the kidneys.
- Amniocentesis or chorionic villous sampling
has been used for prenatal diagnosis.
Treatment
If the hematological changes are mild to moderate
and the patient does not require transfusions,
a period of observation is currently recommended
with frequent blood count checks and yearly
bone marrow examinations.
Observations for the development of secondary
malignancies are also performed. In the short
term, growth factors (such as erythropoetin,
G-CSF, and GM-CSF) can be used to improve blood
counts. Other growth factors for platelet stimulation
are currently under investigation.
Bone marrow transplantation can cure the blood
count problems associated with Fanconi's anemia. A
HLA matched sibling is the best donor source,
although umbilical cord blood cells and
unrelated bone marrow can also be used.
This therapy is very effective, and although
there are associated toxicities, there has been
improvement in the care of Fanconi patients during
the transplant. There is approximately
a 70% success rate for those patients fortunate
enough to have a donor.
Even though a successful bone marrow transplant
can cure the bone marrow problems from Fanconi's
anemia, patients are at risk for other cancers
and must be regularly followed by a physician
(see below).
Prior to bone marrow transplantation, androgen
therapy (oxymetholone, nandrolone decanoate)
combined with low doses of steroids (hydrocortisone,
prednisone) was the standard treatment, and
this approach is currently used if the
patient does not have an appropriate bone marrow
donor.
Typically, 50-75% of patients initially respond
to androgen therapy, however, all patients will
rapidly relapse when the drug is stopped. In
most cases, these drugs eventually become
ineffective.
Symptoms due to low blood counts, such as bleeding,
infections, or symptomatic anemia (fatigue,
shortness of breath, chest pain, dizziness),
are treated with transfusions or antibiotics
as needed. Patients with low neutrophil counts,
who develop a fever, are usually treated with
intravenous antibiotics.
Most patients visit a hematologist, an endocrinologist,
and an ophthalmologist regularly. An orthopedist,
gynecologist, or nephrologist may be seen as
needed.
Prognosis
The reported survival of patients with Fanconi's
anemia is highly varied, ranging from 2 to 25
years. The prognosis is especially poor if blood
counts are low. Survival has likely been improved
with the development and refinement of therapies,
such as bone marrow transplantation.
Although bone marrow transplantation can restore
blood counts, patients with Fanconi's anemia
remain predisposed to a variety of cancers (leukemia,
myelodysplastic syndrome, liver cancer, and
others).
Women with Fanconi's anemia who become pregnant
should be closely followed by a physician as they
often require transfusions throughout pregnancy.
Fertility is decreased in males, although a
small number of Fanconi patients have fathered
children.
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