What Is Membranous Nephropathy?

Introduction

Membranous nephropathy is a disease affecting the kidney.¹ It is an autoimmune disease, meaning that the body’s immune system, that being the body’s defence against foreign substances, attacks the body, as opposed to those foreign substances.² In membranous nephropathy, it is the glomeruli, a network of blood vessels within the kidney, that are under attack by the body.¹ Glomeruli are important for filtering blood in order to make urine. Therefore, in membranous nephropathy, as these glomeruli get damaged, kidney function is impaired.¹ ³ Ultimately, membranous nephropathy can cause nephrotic syndrome, where there’s too much protein in urine and too little protein in blood, commonly causing swelling and high blood pressure, and potentially leading to end-stage kidney disease, where there’s an irreversible decline in kidney function.⁴ ⁵ Treating membranous nephropathy is important for preserving kidney function and preventing complications, often involving a class of medications called immunosuppressants, as well as regular monitoring of the condition. Not all patients require treatment; however, about one-third of patients spontaneously recover.¹

Causes of membranous nephropathy

Membranous nephropathy is a result of a dysfunctioning immune system, where the immune system attacks the body, as opposed to foreign substances.² Specifically, glomeruli, a network of blood vessels within the kidney, are attacked by the immune system.¹ Since these glomeruli are important for filtering blood in order to make urine, their being attacked causes impaired kidney function.¹ ³ ⁶

In the majority of cases of membranous nephropathy, which is about 70 to 80 per cent, have no underlying cause.¹ ⁷

A minority of cases, however, that is about 20 to 30 per cent, have an underlying cause, which may be due to a number of things:¹ ⁷

• Infections
• Drugs
• Cancers
• Autoimmune conditions

Signs and symptoms of membranous nephropathy

Approximately one-third of patients with membranous nephropathy do not experience any signs and symptoms until their condition causes complications.

Around two-thirds of patients with membranous nephropathy have nephrotic syndrome, which can include several signs and symptoms:¹ ⁸

• Swelling
• Fatigue
• Breathlessness
• Frothy urine
• Yellow marks on the body, which may be widespread or solely surround the eyes

Diagnosis of membranous nephropathy

Levels of protein in blood or urine

Measuring levels of protein in blood or urine can indicate how well the kidney is functioning. Though patients do not always present with signs and symptoms of membranous nephropathy, decreased protein in the blood or increased protein in the urine may be present. Furthermore, these measurements can indicate whether nephrotic syndrome has developed.¹

Kidney biopsy

A kidney biopsy involves a doctor taking a sample of tissue from your kidney to be examined with a microscope. Typically, this procedure would involve you lying on your stomach and a doctor inserting a needle into your back. This procedure can cause some pain, so a doctor may prescribe painkillers to help alleviate this, with a day of bed rest being advised. ¹ ⁹

Medical history

A medical history is taken by your doctor during a consultation. This provides an opportunity for your doctor to understand you more, such as any conditions you have, medications you’re taking, your lifestyle, and any signs and symptoms you’re experiencing. The information the doctor gathers during a medical history can help rule out other conditions and confirm the diagnosis of a certain disorder.¹⁰

Management and treatment of membranous nephropathy

Management and treatment of membranous nephropathy can vary depending on the extent to which kidney function is impaired, an individual’s signs and symptoms, and whether a patient is dealing with complications of membranous nephropathy, such as nephrotic syndrome.¹

Frequent monitoring of membranous nephropathy can help ensure the right treatments are provided at the right time. Furthermore, monitoring is important for determining whether treatment is necessary at all, as about one-third of patients spontaneously recover.¹

Immunosuppressants

Immunosuppressants are a class of medication that can be used to treat membranous nephropathy. As membranous nephropathy involves the immune system attacking the body, immunosuppressants can stop this attack, helping the kidneys to return to normal function and preventing signs, symptoms, and complications of membranous nephropathy.¹ ¹¹

However, though immunosuppressants can be of great benefit, they can make one more prone to cancers and infection. So, patients taking these medications should be monitored.¹¹

Diet

Nephrotic syndrome can commonly cause swelling which contributes to fatigue, difficulty in moving, and discomfort. A low-salt diet can help in alleviating swelling due to nephrotic syndrome. A doctor or dietician can help you prepare a plan to change your diet.¹ ¹²

The NHS sets out some tips to help you lower your salt consumption:¹³ 

• Eat salty foods in smaller amounts or less frequently
• Limit the amount of salt you add to your food
• Check the salt content on food packaging
• Try reduced-salt versions of foods
• Add flavour to your food with spices instead of salt
• Limit using too many sauces that may have lots of salt, like ketchup, mayonnaise, brown sauce, gravy, and soy sauce
• Buy tinned foods that use water instead of brine
• Speak to your doctor before taking medications, as some can have a high salt content.

Diuretics

Diuretics are a class of medications which can reduce swelling caused by nephrotic syndrome, particularly when accompanied by a low-salt diet.¹ Diuretics cause you to urinate more, increasing sodium loss through urine.¹⁴

Kidney transplantation

Kidney transplantation is a surgery involving your kidney being removed and replaced by that of a healthy person. This procedure is typically reserved for patients who do not respond to other management and treatment options for membranous nephropathy and are thus at risk of experiencing an irreversible decline in kidney function. Undergoing kidney transplantation means that you have to make prolonged lifestyle changes and take medication to help your body tolerate the new kidney. A doctor can inform you of the changes that may need to be made in your life if you do plan on undergoing kidney transplantation.¹ ¹⁵

Addressing underlying causes

Though only a minority of cases of membranous nephropathy have an identifiable underlying cause, for those cases that do, addressing the underlying cause can allow for recovery. If membranous nephropathy is caused by a disease, then recovery may be achieved by treating said disease, and if membranous nephropathy is caused by a drug, then recovery may be achieved by stopping the use of that drug.¹

Complications of membranous nephropathy

Membranous nephropathy, particularly if untreated, can cause several complications:¹ ¹⁶

• Nephrotic syndrome
• Cardiovascular disease
• Kidney failure

FAQs

How common is membranous nephropathy?

Membranous nephropathy is not a common condition, with 2 to 17 cases per million people in Europe.¹

Can membranous nephropathy be prevented?

As about 80 per cent of people with membranous nephropathy have no identifiable underlying cause for their condition, it can’t necessarily be prevented. However, for a minority of patients whose condition is caused by infections, cancers, and autoimmune conditions, treating these can prevent membranous nephropathy.¹

Can membranous nephropathy be cured?

Outcomes for patients with membranous nephropathy can vary. About one-third of patients will spontaneously recover, not requiring treatment. Some patients can recover with certain management and treatment, whether that be medication, dietary change, or surgery, or a combination of these. Some patients, however, may reach a point of irreversible decline in kidney function.¹

What puts me at risk of getting membranous nephropathy?

Whilst membranous nephropathy can occur in anyone, being assigned male at birth, aged over 40 years, and having another autoimmune condition increases your risk of getting membranous nephropathy.¹ ⁶

Summary

Membranous nephropathy is a disease affecting the kidney, where glomeruli, blood vessels in the kidney that filter blood to make urine, are damaged by the immune system attacking the body, as opposed to foreign substances. Only about 1 in 5 cases have an identifiable underlying cause. In about one-third of cases, the condition resolves by itself. However, the disease can progress to serious complications, commonly nephrotic syndrome, which can cause an irreversible decline in kidney function, potentially leading to cardiovascular disease and kidney failure. Furthermore, signs and symptoms of the condition are not always present but can be and could involve swelling, fatigue, breathlessness, frothy urine, and yellow marks on the body, which may be widespread or solely surround the eyes. Management and treatment could include medication, immunosuppressants and diuretics, and a low-salt diet; kidney transplantation is reserved for patients who do not respond to these therapies.