Minimal Change Disease, also called “glomerulonephritis minimal lesion,” is a kidney disorder that mostly affects children but can also occur in adults. Despite its name, this condition can cause significant symptoms, though the damage to the kidney’s filtering units is so tiny that it can only be seen under a special microscope.
Epidemiology
Minimal Change Disease is one of the most common reasons children develop a condition called nephrotic syndrome, which is a group of symptoms that includes protein leaking into the urine, swelling, and changes in blood cholesterol levels. Between 70% and 90% of children older than one year who develop nephrotic syndrome have Minimal Change Disease as the underlying cause.[2]
In adults, this condition is much less common. Only about 10% to 15% of adults who present with nephrotic syndrome have Minimal Change Disease.[2] The disease affects new children at a rate of about 2 to 7 cases per 100,000 children each year. While the exact number of people living with the condition is not known with certainty, it is estimated that there are between 10 and 50 cases per 100,000 children at any given time.[2]
During childhood, boys are affected about twice as often as girls. However, this gender difference disappears when children reach their teenage years.[2] For adults, the exact incidence remains unknown, though the condition is recognized as less frequent in this age group.[2]
Causes
In most cases, especially in children, the exact cause of Minimal Change Disease remains unknown. Doctors refer to this as idiopathic or primary Minimal Change Disease, meaning there is no clear reason why the immune system starts to harm the kidneys.[2]
However, the disease can sometimes occur as a secondary condition, meaning it develops as a result of another disease or exposure to certain substances. This is more common in adults than in children.[4] Secondary causes of Minimal Change Disease include various infections such as tuberculosis, syphilis, certain bacteria like mycoplasma and ehrlichiosis, and viruses including hepatitis C virus and HIV.[2]
Some medications and substances are also linked to the development of this disease. These include nonsteroidal anti-inflammatory drugs (commonly called NSAIDs), lithium (used to treat certain mental health conditions), antibiotics such as ampicillin and cephalosporins, and even gamma interferon and certain immunizations.[2] Allergic reactions to bee stings, jellyfish (medusa) stings, cat fur, fungi, poison ivy, ragweed pollen, and house dust have also been reported as triggers.[2]
Certain types of cancer, particularly blood cancers like leukemia and both Hodgkin and non-Hodgkin lymphoma, have been associated with Minimal Change Disease. The condition can also appear alongside other kidney diseases such as IgA nephropathy, systemic lupus erythematosus (SLE), type 1 diabetes mellitus, and HIV infection.[2]
Risk Factors
While not everyone with risk factors will develop Minimal Change Disease, certain characteristics and exposures are known to increase the likelihood of developing the condition. It is important to understand that many people with the disease do not have any identifiable risk factors.[21]
Having a personal or family history of kidney disease can increase the risk. Taking certain medications, especially NSAIDs and other drugs mentioned above, may contribute to the development of this condition. Exposure to specific toxins in the environment or workplace can also play a role.[21]
Viral infections such as strep throat, HIV, and hepatitis C, as well as bacterial infections including bacterial endocarditis (an infection of the heart valves), are recognized risk factors. People with autoimmune conditions, where the body’s immune system mistakenly attacks its own tissues, also face a higher risk of developing Minimal Change Disease.[21]
Symptoms
Many people with Minimal Change Disease do not notice any symptoms at first, and the condition may only be discovered during routine urine tests. When symptoms do occur, they are typically related to nephrotic syndrome, which is the main way this disease affects the body.[2]
One of the most noticeable signs is swelling, also called edema. This swelling usually appears around the ankles, feet, and eyes, but it can affect other parts of the body as well. The swelling happens because the kidneys are leaking too much protein into the urine, which reduces the amount of protein in the blood. This imbalance causes fluid to build up in tissues rather than staying in the blood vessels.[4]
The urine may appear foamy or bubbly, which is caused by high levels of protein being lost from the blood into the urine. This protein loss is called proteinuria.[4] Weight gain can occur quickly due to the buildup of excess fluid in the body, not because of increased body fat.[4]
Some patients experience a poor appetite, which can affect their overall nutrition and energy levels.[14] Unlike some other kidney diseases, Minimal Change Disease typically does not reduce the amount of urine produced. It also rarely progresses to kidney failure, which is one reason why it is considered to have a relatively good outlook, especially in children.[14]
Prevention
Because the exact cause of Minimal Change Disease is often unknown, there are no specific measures guaranteed to prevent the condition. However, understanding the risk factors and taking steps to reduce exposure to known triggers may help lower the chances of developing the disease.[2]
Avoiding unnecessary use of medications known to trigger the condition, such as NSAIDs, can be helpful. People should always discuss medication choices with their healthcare provider, especially if they have a history of kidney problems or other risk factors.[2]
Managing infections promptly and thoroughly can also be important. For example, treating strep throat and other bacterial or viral infections early may reduce the risk of complications that could affect the kidneys. Maintaining good overall health through proper nutrition, regular exercise, and avoiding smoking can support kidney health in general.[18]
For people with autoimmune diseases or blood cancers, working closely with healthcare providers to manage these conditions may help reduce the risk of developing secondary Minimal Change Disease. Regular health check-ups and monitoring of kidney function through urine and blood tests can help detect problems early, even if prevention is not entirely possible.[2]
Pathophysiology
Minimal Change Disease causes disruption in the normal functioning of the kidneys, specifically affecting the tiny filtering units called glomeruli. Each kidney contains about one million of these glomeruli, which are responsible for filtering waste products from the blood while keeping important substances like proteins inside the bloodstream.[2]
The glomerulus is made up of three main layers that work together to filter blood. The innermost layer is a thin wall of blood vessels called fenestrated endothelium. The middle layer is the glomerular basement membrane, which acts like a mesh. The outer layer consists of specialized cells called podocytes. These podocytes have large cell bodies and long “foot processes” that wrap around the blood vessels. Between these foot processes are tiny junctions called slit diaphragms that help control what passes through the filter.[2]
Under a regular light microscope, the glomeruli in Minimal Change Disease appear completely normal, which is why the condition is called “minimal change.” However, when examined under a much more powerful electron microscope, doctors can see that the foot processes of the podocytes have become swollen and flattened. This change is called effacement or foot process fusion.[4]
The disease is thought to involve problems with T cells, which are part of the immune system. These T cells may release substances called cytokines that damage the podocytes and their foot processes. This damage leads to a decrease in molecules called polyanions, which normally create a charge barrier that prevents large proteins like albumin from passing through the filter. When this barrier is damaged, albumin and other proteins leak into the urine instead of staying in the blood.[7]
Several specific cytokines have been studied in relation to Minimal Change Disease. Interleukin-12 (IL-12) levels are found to be elevated during active disease and return to normal during remission. Interleukin-4 (IL-4) and a receptor called CD23 are also elevated in the blood. Interleukin-13 (IL-13) has been implicated in causing the podocyte damage and protein leakage seen in the disease.[7]
The filtration system in healthy kidneys is both size-specific and charge-specific, meaning it blocks substances based on their size and electrical charge. The actin cytoskeleton inside podocytes provides structural support to the glomerular basement membrane and helps regulate how substances flow across this barrier. When Minimal Change Disease damages the podocytes, this careful regulation breaks down, leading to increased permeability and protein loss.[2]
In some patients who develop acute kidney injury along with Minimal Change Disease, a substance called endothelin-1 is found at higher levels in the glomeruli, blood vessels, and tubes of the kidney. Components of the slit diaphragm, such as a protein called nephrin, play a major role in preventing protein leakage. Damage to these structures directly contributes to the proteinuria that characterizes the disease.[7]