What Is the Most Common Cause of Nephrotic Syndrome?

Depending on the microscopic picture seen during the kidney biopsy, the nephrotic syndrome is divided into the following types:

Focal segmental glomerulosclerosis (FSGS)

• FSGS is the most common primary cause of nephrotic syndrome in adults accounting for 40 percent of all cases.
• FSGS is a progressive kidney disease that affects specific, segmented areas of the kidney.
• FSGS accounts for 20 percent of all cases in children.
• Causes of FSGS include:
  • Sickle cell disease
  • Kidney Infections
  • Uncontrolled diabetes
  • Obesity
  • Drug interactions, such as excessive intake of nonsteroidal anti-inflammatory drugs (NSAIDs) or chemotherapy drugs
  • Toxic chemical and heavy metal exposure
• Inherited faulty genes (rare)
• FSGS is often diagnosed with a kidney biopsy.
• Even after being treated, patients with FSGS may develop kidney failure and depend on dialysis and kidney transplant for survival.
• Additionally, there is a risk of FSGS in the newly transplanted kidney, which leads to kidney failure.

Minimal change disease

• Minimal change disease, as the name suggests, has very small changes in the kidney that cannot be detected even with a kidney biopsy.
• It is an idiopathic condition, which means there is no clear cause of the abnormal condition.
• Minimal change disease is seen in both children and adults. It is the most common primary cause of nephrotic syndrome in children accounting for more than 90 percent of those diagnosed.
• Many children outgrow minimal change illness, whereas some continue to suffer from it until adulthood.
• Adults have a low incidence, accounting for just 10 to 15 percent of patients with nephrotic syndrome.

Primary membranous neuropathy (PMN)

• PMN refers to alterations in the glomeruli where there may be thickening of the glomerular basement membrane with little or no cellular growth or infiltration.
• PMN is the most common cause of nephrotic syndrome among people who do not have diabetes.
• PMN is seen among all ages but is most commonly seen among people aged 50 to 60 years.
• Almost 30 percent of PMN patients may improve their condition without any medications, but 30 percent may progress into kidney failure and require dialysis or kidney transplant.
• Causes of PMN include:
  • Autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and others
  • Thyroiditis
  • Medicines such as NSAIDs
  • Viral infections such as hepatitis B
  • Tumors

Secondary causes

• Diabetes:
  • Both types I and II diabetes may lead to diabetic kidney disease, which is also referred to as diabetic nephropathy.
  • Diabetes is the most common secondary cause of the nephrotic syndrome.
  • A kidney may get damaged due to high blood sugar levels and high blood pressure.
  • Patients with advanced diabetes have damage to the glomeruli, leading to nephrotic syndrome.
• Systemic lupus erythematosus:
  • Nephrotic syndrome is caused by various types of lupus, which include:
    • Systemic lupus erythematosus
    • Lupus podocytopathy
    • Severe lupus
  • Among these, systemic lupus erythematosus is the most common cause of lupus that causes chronic inflammation to the kidneys.
  • This damages the kidneys and leads to nephrotic syndrome.
• Amyloidosis:
  • Amyloidosis is an accumulation of abnormal protein amyloid in the organs and blood.
  • This protein may damage the kidneys leading to nephrotic syndrome.

Nephrotic syndrome is also known as nephrosis and is a condition caused when the structures in the kidneys that filter blood (glomeruli) are damaged.

• The damaged glomeruli cannot prevent the blood proteins from seeping into the urine.
• Hence, there will be excess excretion of protein in the urine; this condition is known as proteinuria.
• Proteinuria leads to reduced levels of albumin in the blood.

Albumin is an essential protein in the blood that maintains colloid osmotic pressure, which means it maintains the constant movement of fluids in the body. With the loss of albumin, there will be an accumulation of fluid in the body tissues, especially in the legs and face, resulting in swelling.

Kidney damage, if untreated, will worsen over years and result in chronic renal failure.

The first line of treatment for nephrotic syndrome should be managing or treating the underline causes, which reduces symptoms, avoid complications, and postpone kidney failure because there is no definitive cure to nephrotic syndrome. 

• Controlling water and protein intake (as recommended by a doctor)
• Reducing high blood pressure levels with the use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers or diuretics prevents kidney damage. They reduce proteinuria, fluid retention, and swelling.
• Corticosteroids and other immunosuppressive drugs reduce inflammation of the kidneys.
• Intake of vitamin D supplements improves the functionality of the kidneys.
• Dietary modifications such as following a low-sodium diet and limiting the consumption of fats are recommended to reduce proteinuria and fluid retention.
• The use of blood thinners and other anticoagulants reduces the risk of blood clots.

Nephrotic syndrome is seen among all ages although the primary causes may be different. It is seen most frequently among children aged between 18 months and 8 years and is usually diagnosed at three to four years.

Children are most commonly diagnosed with nephrotic syndrome caused by minimal change disease, and adults are the most likely to be diagnosed with nephrotic syndrome due to diabetes.