Minimal Change Disease - Childhood Nephrotic Syndrome

The minimal change disease, also called nephropathy minimal injury, glomerular disease nephrotic syndrome or minimal lesions by minimal injury, kidney disease is a very common in children which is characterized by excessive protein loss in urine.

Edema around eyes
Edema around eyes

Among the signs and symptoms of minimal change disease, the main thing is fluid retention, which usually causes swelling throughout the body, including the face, belly and legs.

The disease minimal injury usually responds well to treatment, especially in children. However, approximately 10% of cases are resistant to drugs and may lead to permanent kidney damage.

In this article we will explain what the minimal change disease, what its causes are, symptoms, diagnostic shapes and the treatments available.

What is the minimal change disease

Nephropathy injury is minimal glomerulopathy, or a disease of the kidney glomeruli. The glomerulus is a microscopic structure, whose main function is to filter the blood. Each of our kidneys has about 1 million glomeruli.

When the glomeruli are healthy, they properly perform their filtering function of the body: the blood reaches the kidneys, and the glomeruli distinguish what is and what is not important for our body. What is unnecessary is eliminated in the urine, which is necessary remains in the blood. The proteins mainly albumin, are important substances for our body, and therefore, under normal conditions, should not be eliminated in the urine as it were any toxic or dispensable substance.

A patient with healthy kidneys lose small amounts of protein in the urine, less than 150 mg per day. The presence of proteins in urine in amounts greater than 150 mg / day is called proteinuria, which is a typical sign of glomerular injury. The more severe glomerular injury, higher proteinuria. Patients with nephropathy minimal injury often lost in the urine over 3500 mg (3.5 grams) of protein per day, reaching in some cases, more than 10,000 mg (10 grams) per day.

The minimal lesion nephropathy is a disease in which there is damage to the glomerular capillary walls, which is effectively the location of the glomerulus occurs where the blood filtration. The damage to the glomerular capillaries causes substances that should remain in the blood end up "slipping" for urine, like a filter full of holes.

Because patients with nephropathy minimal injury had significant proteinuria, it was obvious that they had an injury of the glomeruli, but pathologists were unable to identify it in samples of renal biopsy seen through the light microscope. Therefore, the disease was called nephropathy minimal injuries. Only with the advent of electron microscopy which can magnify an image in more than 10,000 times, compared to about 400 times the optical microscope, it was possible to identify the damage to the glomerular capillaries. The old name, however, remained.


The patient may acquire minimal change disease lifelong (acquired disease) or may already born with it (congenital disease).

The congenital form of minimal injury is the most serious, because in addition to manifest itself in the first months of life, it does not respond to medications commonly used for treatment. The patient is born with a defect in glomerular capillaries and there is nothing that can be done in addition to renal transplantation.

The acquired form of minimal change disease is more common and typically affects children between 1 and 12 years old. Most cases occur before 6 years. Unlike congenital form, nephropathy minimal injury acquired usually responds well to treatment.

The glomerulonephritis acquired by minimal injury is an immunological disease, whose cause is still unclear. The disease seems to have originated in production by T lymphocytes (one of the defense cells of our immune system) of harmful substances to the glomerular capillaries. Nephropathy minimal injury is therefore a disease which arises due to a malfunction of the immune system of the patient.

In children, nephropathy minimal injury usually idiopathic and primary kidney disease, that is, it only affects the kidney and there is no known cause for its emergence. Now, in adults, the disease minimal injury can be caused by other diseases such as lymphoma, leukemia, allergies, infections, excessive use of anti-inflammatories, etc.



The main characteristic of glomerular disease is minimal lesions proteinuria, which, as already explained, is the term used to describe the excessive protein loss in urine.

One of the main signs of the presence of protein in urine is an exaggerated foaming collar type of beer when the patient urine. The more intense proteinuria, will be more foamy urine.

It is important to note that all urine causes some degree of foam on the toilet. However, the foam is marked proteinuria causes clearly more intense than the foam that normally produces its urine.

Proteinuria is not a complication exclusive of minimal change disease. It is usually present in several other diseases that affect the kidneys, including diabetes mellitus. Often, the foamy urine is the earliest symptom of a kidney disease may precede months or years the appearance of other symptoms. So if a sudden you notice that your urine has to foam in an exaggerated way, the ideal is to do a urinalysis to rule out the possibility of existing proteinuria.

Nephrotic syndrome

The foamy urine is not the only sign of protein loss in the urine. As mentioned above, it is normal to lose less than 150 mg per day of protein in urine. Losses from 500 mg per day may already cause noticeable increase in urine foam. Patients with minimal lesions disease usually have proteinúrias of more than 3500 mg per day.

All patients with proteinuria above 3500 mg per day (50 mg/kg in children) are at risk of developing what is called nephrotic syndrome, which is a set of signs and symptoms that occur when the loss of protein in the urine is too large.

The massive loss of protein in the urine causes a reduction of protein concentration in the blood, which in turn leads to fluid retention and water leakage inside the blood vessels to the tissues, mainly skin, causing signs of edema (swellings).

The patient with nephrotic syndrome appears typically with swellings on the face, especially around the eyes, and the lower limbs. Also common is the accumulation of fluid in the abdomen. In men, the scrotum usually become swollen. In more severe cases, fluid leakage affects the lungs and causes frames of fatigue and shortness of breath.

Fluid retention causes weight gain, and it is not uncommon for the patient reaches staying 5 to 10 kg heavier (not fat gain, but retention and liquid).

Several diseases can cause nephrotic syndrome, but nephropathy minimal injury is triggered the leading cause in children, accounting for up to 90% of cases in this age group. In adults, it is less common and accounts for only about 10 to 15% of cases of nephrotic syndrome.


The first step in the diagnosis of nephrotic syndrome, and minimal change disease is to identify and quantitate proteins in urine. Analysis as simple urinalysis and urine 24 hours are often used for this purpose.

About 20 to 30% of patients with minimal change disease also have microscopic hematuria, which is blood in the urine detectable only through laboratory testing.

Blood tests also help. The main findings of the blood test are low albumin values and elevated cholesterol.

Most patients do not present impaired renal function, but 1 in 5 may have acute renal failure, characterized by increasing the value of blood creatinine.

If the patient has generalized edema, and significant proteinuria in the urine tests, the diagnosis of nephrotic syndrome can now be established. The next step is to establish the cause.

The test used for definitive diagnosis is renal biopsy. However, as in children 90% of cases of nephrotic syndrome are caused by minimal change disease, and biopsy is an invasive procedure that entails some risks, most physicians choose the beginning of treatment without a confirmed diagnosis. In children under 12 years, the biopsy is reserved for cases that do not respond to treatment or if the doctor has any reason to suspect that the nephrotic syndrome child has other cause than nephropathy minimal injury.

In adults the situation is different. As there are dozens of different causes of nephrotic syndrome and none of them is markedly more common than others in this age group, it is impossible to define a diagnosis and establish a therapeutic strategy without the biopsy. So for a definitive diagnosis of the cause of nephrotic syndrome in adults, renal biopsy is usually the best option.


The initial treatment of disease minimal damage is done with glucocorticoids, typically prednisone or prednisolone. The doses and the time of treatment most used are:
  • Children - 2 mg / kg orally (up to 60 mg) every other day for 6 weeks. After the first 6 weeks the dose is reduced to 1.5 mg / kg (maximum dose 40 mg) for 6 more weeks. After these 12 weeks, the dose should be reduced gradually over the next 2 or 3 months until complete suspension*.
  • Adults - 1 mg / kg per day orally (maximum dose 80 mg) for 12 to 16 weeks. After this period, gradually reducing the dose over 6 months until complete suspension*.

* This process of gradual reduction of the dose of steroids is called weaning and must always be respected, as the abrupt withdrawal of corticosteroids after prolonged treatment can cause serious adverse effects.

Over 90% of patients experience remission of proteinuria, and the vast majority do within the first 4 weeks of treatment. However, about half of patients may have a relapse of the disease after the end of treatment, the complete suspension of corticoids. In this case, a new course of corticosteroids is indicated.

Because steroids are responsible for a lot of side effects, especially when used for a prolonged period, the ideal is to change the treatment in patients with multiple relapses (which corresponds to about 20% of the cases), so as to minimize the toxic effects of long term corticosteroids. In adults, the drug of choice for the frequent relapses is cyclophosphamide, while in children is mycophenolate mofetil.

As explained above, cases of congenital nephrotic syndrome do not respond to drug treatment.

In adults with secondary minimal lesion disease to some disease, the treatment of nephrotic syndrome goes through your treatment early disease. For example, if the patient developed minimal change disease because of a lymphoma above, the treatment is directed to nephropathy minimal injury, but against the lymphoma. The lymphoma cure leads to cure minimal change disease. If the frame has been caused by excessive use of anti-inflammatory treatment is simply the suspension of anti-inflammatories.

The patients who can not get control of their nephrotic syndrome over the years is at high risk of developing chronic renal failure.

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