Usmle hot points review
Danil Hammoudi.MD
1/
Fanconi’s syndrome
renal tubular defect, spare the glomeruli but result in a generalized pattern of tubular dysfunction may lead to the loss of:
· Phosphate
· Calcium
· Glucose
· Amino acids
Result : OSTEOMALACIA and RICKETS
·
excessive urine production and
urination
·
excessive thirst;
·
dehydration;
·
constipation;
·
anorexia nervosa;
·
vomiting;
·
elevated levels of glucose, phosphate,
calcium, uric acid, amino acids, and protein (especially beta2-microglobulin and
lysozyme) in the urine;
·
elevated levels of chloride
·
decreased levels of phosphate and calcium
in the blood;
·
excessively acidic
blood.
This reabsorption step is
defective in Fanconi's syndrome.
As a consequence, substances
that are normally reabsorbed, like glucose, amino acids, small proteins, water,
calcium, potassium, magnesium, bicarbonate, and phosphate, are lost and the body
becomes overly acidic.
The most noticeable indirect
consequences of impaired reabsorption are the bone diseases, rickets and
osteomalacia
. Rickets affects children
and is associated with bone deformities, failure to grow, and difficulty
walking.
If a person acquires Fanconi's syndrome
as an adult, the bone disease is termed osteomalacia and is accompanied by
severe bone pain and spontaneous fractures.
Unlike rickets due to
malnutrition, these diseases cannot be
reversed with vitamin D.
Muscle weakness and
occasional paralysis are other indirect consequences of the ineffective
reabsorption
The genetic diseases known to
give rise to Fanconi's syndrome are
·
cystinosis (the most common
cause in children),
·
galactosemia,
·
glycogen storage
disease,
·
hereditary fructose
intolerance,
·
Lowe syndrome,
·
Wilson disease,
·
tyrosinemia,
·
medullary cystic
disease,
·
vitamin D dependency,
·
familial idiopathic Fanconi's
syndrome
Environmental assaults that
cause Fanconi's syndrome include :
·
exposure to heavy metals (like cadmium, lead,
mercury, platinum, uranium),
·
certain drugs (like outdated tetracycline and
gentamicin),
·
other substances (like Lysol, paraquat,
toluene, the amino acid lysine taken as a nutritional supplement),
·
kidney transplantation
Fanconi's syndrome is also
known as Fanconi syndrome, renal Fanconi syndrome, Fanconi renaltubular
syndrome, and Lignac-de Toni-Debre-Fanconi syndrome. Fanconi's anemia is,
however, a totally different disease.
CAUSES:
1. Primary Fanconi
Syndrome
2. Secondary Fanconi
Syndrome
|
Fanconi’s syndrome
:aquired
· An inherited blood disease
· bone marrow fails to produce all types of blood cells.
· Lack of white blood cells results in predisposition to infections,
· while lack of platelets and red blood cells 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.)
deToni-Debre-Fanconi
syndrome
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.
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),
·
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.
Many different diseases can cause Fanconi syndrome.
The underlying disease should be treated if there
is a treatment available. For example:
Most disorders causing Fanconi syndrome cannot be treated directly.
In these cases, the symptoms of the disease are treated instead.
Symptomatic therapy
includes:
Prognosis
Fanconi's syndrome can be
reversible. Fanconi's syndrome caused by kidney transplantation usually reverses
itself within the first year after transplant surgery.
When caused by a toxin in the
environment, Fanconi's syndrome generally can be reversed by removing the
causative agent from the patient's environment.
If it is caused by a genetic disease, it
can usually be reversed by treating the disease.
However, if Fanconi's
syndrome is not treated or if treatment is unsuccessful, the kidneys can fail.
• Acidosis
Condition
where the body is more acidic than normal; associated with headache, nausea,
vomiting, and visual disturbances.
• Fanconi's
anemia
An
inherited form of aplastic anemia.
• Filtrate
The
part of filtered material that flows through the filter.
• Idiopathic
Refers
to a disease of unknown cause.
• Polydipsia
Excessive
thirst.
• Polyuria
Excessive
production of urine.
TO
RESUME
I.
Pathophys
A.
Deficient Renal Tubular excretion
B.
Results in:
1.
Aminoaciduria
2.
Glycosuria
|
I.
GLYCOSURIA
II.
Hyperglycemia Causes of glucose in
urine
A.
See Hyperglycemia
HYPOPHOSPHATEMIA
I.
Causes
A.
Starvation
C.
Total Parenteral
Nutrition (TPN)
D.
Insulin
E.
Nasogastric Suction (NG Suction)
F.
Diuretics
G.
Vomiting
H.
Vitamin D deficiency
I.
Hypoparathyroid
J.
Pseudohypoparathyroid
K.
Medications
1.
Corticosteroids
2.
Aluminum Hydroxide antacids
L.
Gram negative sepsis