Minimal Change Disease (MCD) is a disorder of the kidneys that affects the glomeruli, the tiny filtering units within the organ. It is the most frequent cause of nephrotic syndrome in children, though it also affects adults. The name refers to how the kidney tissue appears under a standard light microscope, where the filtering structures show no observable damage. MCD is characterized by a significant loss of protein from the blood into the urine, which disrupts the body’s fluid balance.
Defining Minimal Change Disease
The true pathology of the disease is revealed only when the tissue is examined using an electron microscope. This advanced imaging shows damage to specialized cells called podocytes that wrap around the glomerular capillaries. These cells possess delicate, finger-like extensions known as foot processes, which normally form the final filtration barrier. In MCD, these foot processes lose their distinct structure and appear to merge or flatten, a change known as effacement or fusion.
This structural rearrangement compromises the integrity of the kidney’s filtration barrier. The barrier, which typically prevents large proteins like albumin from passing into the urine, becomes leaky. Consequently, massive amounts of protein escape from the bloodstream into the urine, a condition known as massive proteinuria.
Recognizing the Signs
The functional failure of the kidney filter leads to a collection of symptoms known as nephrotic syndrome, the most noticeable of which is pronounced swelling, or edema. This fluid retention often appears first around the eyes, especially in the morning, and later affects the lower extremities like the ankles and feet. Patients may also experience rapid weight gain due to the significant accumulation of fluid throughout the body.
The excessive loss of protein in the urine can cause the urine to appear frothy or foamy. The loss of protein from the blood also triggers the liver to produce more cholesterol, leading to high levels of fats in the bloodstream, a condition called hyperlipidemia.
Internally, the low levels of protein in the blood, known as hypoalbuminemia, reduce the pressure that holds fluid within the blood vessels. This shift in fluid dynamics is what causes the fluid to leak out of the vessels and collect in the body’s tissues, resulting in the visible edema. While these signs can be quite severe, the actual ability of the kidneys to clear waste products from the blood often remains within a normal range in MCD.
Diagnosis and Identification
A physician typically begins the diagnostic process by screening the urine for protein using a simple dipstick test. If this test is positive, a more precise measurement of protein loss is often conducted using a 24-hour urine collection or a spot urine sample to calculate the protein-to-creatinine ratio. Blood tests are concurrently ordered to confirm the other features of nephrotic syndrome, specifically low blood albumin and high cholesterol levels.
While the combination of these findings strongly suggests MCD, particularly in young children, a definitive diagnosis relies on a kidney biopsy. During this procedure, a small sample of kidney tissue is removed and examined under different types of microscopes. The biopsy is performed to rule out other, more serious causes of nephrotic syndrome that may require different treatment approaches.
In children, a biopsy is often deferred if they respond quickly to initial treatment. However, it is more commonly performed in adults or in patients who do not respond to initial therapy.
Treatment Approaches and Management
The standard first-line treatment for Minimal Change Disease involves the use of corticosteroids, such as Prednisone. This medication is highly effective for MCD, with approximately 90% of children achieving complete remission, meaning the protein loss stops. The treatment course requires a sustained period of high-dose medication, followed by a gradual reduction to minimize side effects.
If a patient’s condition is steroid-dependent, or if they experience frequent relapses, additional immunosuppressive agents may be introduced. These second-line therapies can include medications like cyclosporine, tacrolimus, or cyclophosphamide, which help to suppress the immune system and reduce the need for long-term high-dose corticosteroids. In some complex cases, a biologic agent like rituximab may be used.
Supportive care is also an important aspect of managing the disease, especially during periods of relapse. Diuretics are frequently prescribed to help the body excrete the excess fluid that causes edema. Dietary adjustments, such as reducing salt intake, can further help control fluid retention. The long-term outlook for individuals with MCD is generally favorable, as the condition rarely progresses to permanent kidney failure.