Usmle hot points review
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:
· Amino acids
Result : OSTEOMALACIA and RICKETS
· excessive urine production and urination
· excessive thirst;
· anorexia nervosa;
· 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),
· glycogen storage disease,
· hereditary fructose intolerance,
· Lowe syndrome,
· Wilson disease,
· 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· certain drugs (like outdated tetracycline and gentamicin),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.
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.)
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:
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.
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.
The part of filtered material that flows through the filter.
Refers to a disease of unknown cause.
Excessive production of urine.
A. Deficient Renal Tubular excretion
B. Results in:
II. Hyperglycemia Causes of glucose in urine
A. See Hyperglycemia
C. Total Parenteral Nutrition (TPN)
E. Nasogastric Suction (NG Suction)
H. Vitamin D deficiency
2. Aluminum Hydroxide antacids
L. Gram negative sepsis