Fanconi's syndrome;
familial
Alternative names:
deToni-Debre-Fanconi
syndrome
Definition:
Fanconi syndrome
is an impairment in proximal tubular function of the kidney.
This impairment causes certain compounds, which should be
absorbed back into the bloodstream by the kidneys, to be excreted
in the urine instead. Some compounds that may be lost in the
urine include glucose, amino
acids, uric acid, and phosphate. Loss of these compounds
can cause problems such as growth failure, decreased bone
mineralization (rickets),
and abnormal bone mineralization (osteomalacia). Type two
renal tubular acidosis (RTA) occurs when too much bicarbonate
is excreted in the urine, causing excess acid in the blood
(acidosis). Another problem that may result is dehydration
caused by excess urination.
Causes:
Fanconi
syndrome can be genetic or acquired later in life. Common
causes of Fanconi syndrome in children are genetic defects
impairing the body’s ability to break down certain compounds,
such as the amino acid cystine (Cystinosis), fructose (fructose
intolerance), galactose (galactosemia), and glycogen (glycogen
storage diseases). Cystinosis is the most common cause of
Fanconi syndrome in children. Lowe’s disease (oculocerebrorenal
syndrome), a rare genetic disorder of the eyes, brain, and
kidneys, can also cause Fanconi syndrome. Another genetic
defect that can cause Fanconi syndrome is Wilson’s disease,
which causes copper to collect in the kidneys, liver, eyes,
and other organs. Similarly, exposure to heavy metals, such
as lead poisoning, can cause Fanconi syndrome, even when there
is no genetic disease.
In
adults, Fanconi syndrome can be caused by various acquired
disorders that damage the tubules of the kidneys. As in children,
this damage can be caused by exposure to heavy metals such
as lead, mercury, and cadmium. The kidneys can also be damaged
by prescribed drugs such as cidofovir (used to treat AIDS-related
cytomegalovirus disease), gentamicin, tetracycline used after
its expiration date, and azathioprine (used to suppress the
immune system after organ transplantation or to treat certain
autoimmune disorders). Kidney damage leading to Fanconi syndrome
can also be caused by dysproteinemias, diseases in which there
are abnormal protein deposits in the kidney. These include
multiple myeloma, light chain deposition disease, and primary
amyloidosis. It can also occur as a result of a kidney transplant.
Sometimes, in both children and adults, the cause of Fanconi
syndrome is not known.
Symptoms:
- Excess amounts
of the following substances in the urine: amino acids,
glucose, phosphate, magnesium, potassium, bicarbonate and
sodium.
- Growth failure
- Rickets in children
- Osteomalacia
in adults (abnormal bone mineralization, causing an increased
incidence of fractures)
- Dehydration
due to excess urination
Treatment:
Many
different diseases can cause Fanconi syndrome. The underlying
disease should be treated if there is a treatment available.
For example:
- Wilson’s disease
is treated with D-penicillamine, which binds excess copper
in the blood
- Cystinosis is
treated with cysteamine, which removes cystine from the
body.
Most
disorders causing Fanconi syndrome cannot be treated directly.
In these cases, the symptoms of the disease are treated instead.
Symptomatic therapy includes:
- Alkali therapy,
which treats acidosis by increasing the pH of the blood
- Replacement
of electrolytes such as potassium, phosphate, calcium and
magnesium
- Supplementing
the diet with Vitamin D to prevent rickets and osteomalacia
Support Groups:
Support
groups exist for many of the diseases that can result in Fanconi
syndrome.
Prognosis:
The prognosis depends
on the underlying disease.
Calling your
health care provider:
Call your health
care provider if dehydration or muscle weakness occurs.
Update Date: 05/08/00
Updated
by: Debbie L. Cohen, Nephrology Fellow, Renal & Electrolyte
Division, Hospital of the University of Pennsylvania, VeriMed
Health Network
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