Minimal change disease (MCD) is a kidney condition characterized by damage to the glomeruli, the small filtering units in the kidneys, which leads to nephrotic syndrome. MCD is the most frequent cause of nephrotic syndrome in children, accounting for 70-90% of cases, but it also affects adults, representing 10-15% of adult diagnoses. The condition’s name comes from the fact that under a standard light microscope, the kidney tissue appears normal or shows only very subtle abnormalities.
Symptoms and Causes
The onset of symptoms in minimal change disease can be sudden. The most prominent sign is significant edema, which is swelling caused by fluid retention. This swelling is often first noticed around the eyes, ankles, and legs, but can become more widespread. Another common symptom is foamy-appearing urine, a result of large amounts of protein leaking into the urine (proteinuria), which also leads to rapid weight gain.
In most cases, particularly in children, minimal change disease is idiopathic, meaning its specific cause cannot be identified. Researchers believe it may be linked to a dysfunction in T-cells, a type of immune cell, but the exact mechanism remains unclear. For a smaller number of individuals, the disease occurs secondary to other factors. These can include allergic reactions, recent infections, or the use of certain medications, most notably nonsteroidal anti-inflammatory drugs (NSAIDs). In some adult cases, MCD has been associated with specific types of cancer, such as Hodgkin lymphoma.
The Diagnostic Process
Diagnosing minimal change disease involves evaluations to confirm nephrotic syndrome and rule out other kidney disorders. The process begins with non-invasive tests. A urinalysis is performed to detect heavy proteinuria, a hallmark of the condition. Blood tests are also conducted to check for low levels of albumin (hypoalbuminemia) and to assess overall kidney function, which is often normal in MCD.
While initial tests can strongly suggest MCD, a definitive diagnosis requires a kidney biopsy. This procedure involves taking a small sample of kidney tissue for examination. When the tissue is examined with a powerful electron microscope, a characteristic abnormality becomes clear. The podocytes, specialized cells that wrap around the capillaries of the glomeruli, show a flattening or “effacement” of their foot processes, which disrupts the kidney’s filtering barrier.
Treatment Approaches
The primary goal of treatment for minimal change disease is to stop the leakage of protein into the urine and induce remission, a period where symptoms disappear. The standard first-line treatment for both children and adults is a course of corticosteroids, most commonly a medication called prednisone. The response to this therapy is generally positive, especially in children, with a large majority experiencing a reduction in proteinuria and entering remission.
If a patient does not respond to corticosteroids or experiences significant side effects, other treatment strategies are considered. These second-line therapies involve different types of immunosuppressive medications, such as cyclophosphamide or calcineurin inhibitors. Supportive care is used to manage the symptoms. Diuretics may be prescribed to help reduce the body’s excess fluid and swelling, and a low-salt diet is also recommended to help control fluid retention.
Prognosis and Relapse Management
The long-term outlook for individuals with minimal change disease is very good. Unlike many other kidney diseases, MCD rarely progresses to cause permanent kidney damage or chronic kidney failure. Most patients respond well to initial treatment and maintain normal kidney function. Many children eventually outgrow the condition and stop experiencing relapses during their teenage years.
A common feature of minimal change disease is the potential for relapse, where symptoms return after a period of remission. These relapses are often triggered by common events, such as viral infections. The management for a relapse is another course of corticosteroids to bring the disease back into remission. While some individuals may experience infrequent relapses, others are considered “frequent relapsers” and may require longer-term treatment plans with steroid-sparing medications.