Minimal change disease

Minimal change disease or nil disease (lipoid nephrosis) is a disease of the kidney which causes nephrotic syndrome and usually affects children (peak incidence at 2-3 years of age).

Minimal change disease is most common in very young children, but can occur in older children and adults. It is by far the most common cause of nephrotic syndrome (NS) in children under 10 years of age, accounting for the majority (about 90%) of these diagnoses. Among teenagers who develop NS, it is caused by minimal change disease about half the time. It can also occur in adults, but accounts for less than 20% of adults diagnosed with NS. Among children less than 10 years of age, boys seem to be more likely to develop minimal change disease than girls.

Symptoms

The symptoms are proteinuria (leakage of protein into the urine) and edema (water retention). Nephrotic syndrome (NS) is a general term that refers to the loss of protein in the urine. Many conditions are categorized as nephrotic syndromes -- minimal change disease is unique, because it is the only one lacking any evidence of pathology on light microscopy. When viewed with an electron microscope, it discloses diffuse loss of visceral epithelial cells (podocyte) foot processes.

When protein is lost in the urine, its blood concentration decreases, allowing water to move into other areas of the body, which leads to swelling known as edema. Edema is commonly observed in the feet and legs, in the belly or abdomen, and around the eyes, but can occur anywhere, especially in response to gravity. Additionally, because of this extra fluid that stays in the body, people often gain weight and experience fatigue -- in many patients, for example, their usual clothes and shoes will no longer fit. Some people notice that their urine becomes more frothy, and may find that they urinate less often.

Causes

Minimal change disease can be associated with food allergies, medications, or hematologic malignancies, or it can occur idiopathically. The pathology does not appear to involve complement, immunoglobulins, or immune complex deposition. Rather, an altered cell-mediated immunologic response with abnormal secretion of lymphokines by T cells is thought to reduce the production of anions in the glomerular basement membrane, thereby increasing the glomerular permeability to serum albumin through a reduction of electrostatic repulsion. The loss of anionic charges is also thought to favor foot process fusion. With minimal change disease the kidney tissue appears normal under a light microscope, but shows podocyte foot process effacement under an electron microscope.

Treatment

Prednisone is prescribed along with a blood pressure medication, typically an ACE inhibitor such as lisinopril. Some nephrologists will start out with the ACE inhibitor first in an attempt to reduce the blood pressure's force which pushes the protein through the cell wall in order to lower the proteinuria. In some cases a corticosteroid may not be necessary if the case of minimal change disease is mild enough to be treated just with the ACE Inhibitor. Often the liver is overactive with minimal change disease in an attempt to replace lost protein and over produces cholesterol. Therefore a statin drug is often prescribed for the duration of the treatment. When the urine is clear of protein, the drugs can be discontinued. 50% of patients will relapse and need further treatment.

Minimal change disease usually responds well to initial treatment, with the symptoms of nephrotic syndrome (NS) typically going away, but this can take weeks to months. Younger children, who are more likely to develop minimal change disease, usually respond faster than adults. In 2 out of 3 children with minimal change diease, however, the symptoms of NS can reoccur, called a Relapse, particularly after an infection or an allergic reaction. This is typical, and usually requires additional treatment. Many children experience 3 to 4 Relapses before the disease starts to go away. Some children require longer term therapy to keep MCD under control. It appears that the more time one goes without a Relapse, the better the chances are that a Relapse will not occur. In most children with minimal change disease, particularly among those who respond typically, there is minimal to no permanent damage observed in their kidneys.

With steroid treatment, the symptoms of nephrotic syndrome (NS) will go away, called remission, in the majority of children with minimal change disease. This typically occurs faster, over 2 to 8 weeks, in younger children, but can take up to 3 or 4 months in adults. Typically the dose of steroids will initially be fairly high, lasting 1or 2 months. At some point after the urine protein levels have become normal again, the dose of steroids might be switched to an every-other-day schedule, then very slowly reduced over the course of several months. It is very important to taper, or gradually reduce, the dose of steroids. The body does not respond well to a sudden discontinuation of steroids, and this might also trigger a relapse, or return of NS symptoms. Giving steroids initially for a longer period of time is thought to reduce the likelihood of relapse. The majority of children with minimal change disease will respond to this treatment.

Even among those who respond well to steroids initially, it is common to observe periods of relapse (return of NS symptoms). Because of the potential for relapse, your physician might prescribe and teach you how to use a tool to have you check urine protein levels at home. Two out of 3 children who initially responded to steroids will experience this at least once. Typically the steroids will be restarted when this occurs, although the total duration of steroid treatment is usually shorter during relapses than it is during the initial treatment of the disease.

Though steroids are the first-line therapy for minimal change disease, they have a significant number of side effects, inlcuding, but not limited to, suppression of the immune system, increase risk for diabetes, weight gain, increased risk for high blood pressure, osteoporosis, and cataract formation. Steroids also raise a person's cholesterol.

If steroids are not successful, or are contraindicated for various reasons, alternate therapies exist, including cyclosporine, tacrolimus, and mycophenilate mofetil (Cellcept). Of these, Cellcept offers the best "bang for buck", in terms of least side effects, and allowance of reducation in steroid dosage. It must be noted, however, that the immune system of suppresion of Cellcet and Prednisone are ADDITIVE, and place the person at significant risk of infection.