Kidneys, the bean-shaped organs of the body, perform the vital function of filtering blood by getting rid of waste products and excess fluids. While the purified blood is sent back to circulation, the waste products are excreted as urine. Minimal change nephrotic syndrome also called minimal change disease (MCD) is a damage to the kidney’s filter, called glomeruli.
The kidney performs this filtration function multiple times a day, pumping around one liter of blood every minute. The damage of the filtration units of the kidneys leads to nephrotic syndrome, which is a group of symptoms involving loss of protein through the urine.
MCD and nephrotic syndrome
“The kidneys have over ten lakh filtration units called nephrons, each of which has a small filter called glomerulus, which are a cluster of blood vessels that filter blood and send the waste products through the bladder as urine” says Dr Santosh Kumar, senior nephrologist, Kamineni Hospitals, Hyderabad.
Elaborating further, Dr Santosh says that the glomerulus has walls which are permeable and only filter small molecules like water and waste out of the body, while larger molecules are retained. In nephrotic syndrome, these filters get damaged and lose their permeability, allowing larger molecules like proteins to get leaked into the urine. The loss of protein through urine is called proteinuria.”
One of the symptoms of MCD, is the swelling in the tissues, which is due to the fluid build-up in the body’s tissues. This has a direct link with protein loss. It is the proteins that help in keeping the fluid in the bloodstream, and the decline in proteins leads to fluid leak into the tissues causing swelling or edema.
Minimal change disease: what’s in the name?
“While a healthy kidney allows below 1 gram of protein to be leaked into the urine, in nephrotic syndrome, more than 3.5 grams of protein are lost from the urine in a day,” says Dr Haresh Dodeja, director, Nephrology & Transplant services, Fortis Hospital, Mulund, Mumbai.
Shedding light on the peculiar name of the condition, Dr Dodeja says that the damage to the glomeruli cannot be seen under a regular light microscope making the kidneys look the same on a regular microscope- hence the name minimal change. It requires a powerful electron microscope to spot the damage to the glomeruli.
MCD more common in children
Only 10% of cases of nephrotic syndrome are due to MCD in adults, while in children, MCD is the most common cause of nephrotic syndrome.
According to Dr Santosh, sometimes the cause of minimal change disease can be an autoimmune response, where the body starts producing antibodies against the glomerular membrane, causing it to become porous.
“As children’s immune system is naïve to new infections, it can trigger a mal-immunological response. In adults the immune system is more regulated due to exposure to infections over time,” explains Dr Santosh.
What causes minimal change disease?
Minimal change disease can have primary and secondary causes.
“The cause is categorized as primary, when the cause is unknown (idiopathic). If the cause is secondary, it means that the condition has occurred due to underlying conditions like cancers, infections like malaria, tuberculosis, syphilis, or over use of certain medicines like painkillers,” says Dr Sharad Sheth, consultant and head, Nephrology, Kokilaben Dhirubhai Ambani Hospital, Mumbai.
“MCD due to primary causes is more common and is usually seen among children. Secondary causes are rare and are mostly seen among adults.” notes Dr Sheth.
Diagnosing Minimal change nephrotic syndrome
According to Dr Dodeja, a kidney biopsy is the gold standard for diagnosing minimal change disease.
“In children, a biopsy is not usually done, as nephrotic syndrome mostly indicates MCD in children. In adulthood, nephrotic syndrome may have other causes, entailing a biopsy,” he says.
Dr Dodeja further adds that, if a child isn’t responding to treatment, or the condition keeps relapsing, then a biopsy is done to probe further.
Minimal change disease treatment
“Minimal change disease has a good prognosis and is usually treated with steroids which can include tablets and injections. If the cause is an autoimmune pathology, immunosuppressants are also prescribed, says Dr Santosh.
Dr Dodeja adds that the condition is cured in more than 90% of cases, in response to steroids and the chances of the person developing kidney failure are low (2%).
Relapse in minimal change disease is common, and often the same treatment with steroids is repeated.
According to a 2019 study on Management of Adult Minimal Change Disease published in the Clinical Journal of the American Society of Nephrology, relapses occur in 65%–80% of adults with minimal change disease, with most relapses being seen within the first 3–6 months after a remission. Most adults have only an occasional episode of relapse, that is less than or equal to one per year.
People who face relapse two or more times within 6 months or four or more times within 12 months are “frequent relapsers,” and those having two relapses with steroid taper or within 1 month of ending therapy are “steroid dependent.” The chances of relapse are lower in children.
Takeaways
- Minimal change disease is caused by the damage to the glomerulus, the filtering units of the kidneys, leading to nephrotic syndrome.
- Nephrotic syndrome is characterized by the loss of proteins in the urine, causing swelling.
- Biopsy is the gold standard for diagnosing MCD.
- Minimal change nephrotic syndrome is treated by steroids and immunosuppressants.
