Introduction

Fibrillary glomerulonephritis (FGN) is a rare but serious condition that affects the kidneys’ filtration unit, known as glomeruli. These structures work like sieves by removing waste products from the blood and preventing big proteins from entering the urine.¹

In FGN, glomerular function is reduced as a result of fibril deposits in the glomeruli. These fibrils, which are immunoglobulin proteins with an elongated structure, become trapped within the glomerular tissue and hinder filtration.² Their presence may also lead to inflammation and leakage of proteins (proteinuria) and some blood in the urine (haematuria).

People with FGN will present with symptoms of cloudy urine (proteinuria) or blood in their urine. They may also experience some swelling in their legs and an increase in their blood pressure due to poor kidney function.² Laboratory tests are carried out to establish kidney function and the extent of renal insufficiency that the person is experiencing. All these tests do not allow for exact diagnosis, this can only be done by observing a kidney biopsy sample under a specialised type of microscope known as an electron microscope.² The latter uses a beam of electrons for bigger image magnification compared to a regular light microscope.

Scientists are still unaware of the exact reason these fibrils are deposited in glomeruli, but a link to cancer and autoimmune disorders is suspected.²

There are currently no treatments for FGN, and the management strategies aim at controlling the severity and progression of symptoms, improving the person's quality of life, and maintaining kidney function from further deterioration. Certain medications like angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) are often used as they aid in reducing blood pressure and proteinuria and are known for protecting the kidneys.³ Often, immunosuppressive therapy with drugs like rituximab might be used, although results have been mixed so far.

Progression of FGN leads to end-stage kidney disease and the need for dialysis and a kidney transplant.

Initial assessment

Baseline clinical evaluation

A baseline assessment is carried out upon initial presentation and includes obtaining a detailed medical history. The clinician will ask about current health issues and medications, any coexisting diseases, and about family history and risk factors that increase the chance of having FGN and any of its complications.

A physical assessment will also be taken. This will include measuring pulse, blood pressure, temperature, respiratory rate and palpating the kidneys. Legs will also be observed for any signs of swelling resulting from fluid buildup.

Baseline laboratory tests

Some laboratory tests can be ordered to estimate renal function and the extent of damage currently present.

Urinalysis is carried out by collecting a urine sample and analysing it to check for the presence of any proteins, blood or bacteria.

Blood samples are also taken to measure the levels of creatinine, electrolytes, blood urea nitrogen (BUN), and estimated glomerular filtration rate (eGFR). High levels of creatinine and BUN, accompanied by a low eGFR mean the kidneys are not working properly.

The clinician might test for biomarkers of autoimmune disease, like antinuclear antibody (ANA) or antineutrophilic cytoplasmic antibody (ANCA), if FGN is suspected to be of autoimmune origin.^4,5

Imaging studies

Some imaging techniques, such as renal ultrasound or MRI, might be requested to check the current appearance and structure of the kidneys. This will look for any anomalies in structure, swelling or signs of obstruction like stones or tumours.

Monitoring parameters

Once a diagnosis is confirmed, the clinician and patient will have a discussion to go over their results, the progression of their disease and what options they have. They will also go over the necessary tests required to monitor their condition and response to any treatment that might be initiated. 

Kidney function tests

Most of the kidney tests that will be performed are those done during the initial assessment. Samples will be collected at regular intervals and the results compared to the baseline ones. These will look at creatinine levels and eGFR, and other markers of kidney function.

Measuring protein levels in the urine will also be required to estimate how fast the kidneys are deteriorating.

Blood pressure monitoring

Hypertension is caused by kidney dysfunction and will aggravate the renal damage if left untreated. It is also a risk factor for many other comorbidities, like heart disease and stroke.

It is important to keep blood pressure below 140/90 mmHg through healthy lifestyle modifications or the use of medications. As previously mentioned, drugs such as ACEi and ARBs are used to control blood pressure and preserve kidney function simultaneously.

Patients are also encouraged to monitor their blood pressure at home and report any high figures that may occur despite treatment and lifestyle changes.

Monitoring for complications

Electrolyte imbalances

Kidneys are responsible for regulating the levels of some electrolytes, like potassium and sodium in the body. FGN can cause some imbalances like hyperkalaemia (high potassium) or hyponatremia (low sodium) since the kidneys cannot filter blood properly and are unable to maintain the appropriate levels of these electrolytes. Hyperkalemia is dangerous as too much potassium can cause heart problems like arrhythmias, and hyponatremia can result in swelling.

Anaemia

Kidneys release a hormone called erythropoietin (EPO) which stimulates the production of red blood cells by the bone marrow. If the kidneys are damaged, EPO levels are low, and blood cell production is reduced. This may result in anaemia, where the patient will constantly feel tired and might experience difficulty breathing as their blood oxygen levels are low.

Treatment evaluation

Although no actual treatment is yet available for FGN, drugs like immunosuppressants, steroids, cyclophosphamide and rituximab have been used in patients with this disease.^6,7

If a person receives any drug therapy, they should also be monitored for treatment effectiveness and side effects.

Effective treatment is indicated by decreases in symptoms like proteinuria and haematuria. Disease progression should also slow down, and the incidence of complications should be lower.

If immunosuppressants are used, monitoring for infections and malignancy should also be considered, as these medications dampen the body’s immune response.

Long-term use of steroids is associated with multiple side effects, like increased blood pressure and glucose levels. They may also make their user more prone to catching infections due to their effect on the body’s immune response.⁸

In general, any new or worsening side effect needs to be discussed with the doctor to obtain their advice on how to deal with it. 

Patient education and self-monitoring

It is crucial that a person with FGN fully understands their condition, its complications and how to control them. It is important that any treatment is followed as prescribed and adhered to. Any unpleasant side effects should be reported to the clinician to try to work around them, either by adjusting the doses or stopping the treatment.

Certain lifestyle modifications might also be beneficial in curbing the progression of the disease and reducing the severity of the complications. Consuming a healthy low-sodium diet and exercising regularly are highly recommended.

Patients are also encouraged to keep an eye on their symptoms and be aware of any signs of further deterioration or any new complications. Conducting home blood pressure monitoring also allows them to be in control of their health and helps them spot any increases which may not be accompanied by any symptoms.

Long-term follow-up

FGN will almost always progress into end-stage kidney disease. Patients should be aware of what this means for them and what to expect. It is good to be familiar with the procedures of dialysis and kidney transplant and know what benefits and risks they carry. Patients should approach their care provider if they have any concerns or worries, as they can provide them with information and support to prepare them for this. 

Summary

Fibrillary glomerulonephritis is a rare renal condition that affects the kidneys’ ability to filter blood contents properly at the glomerular level. It is caused by the presence of fibrillary proteins that hinder the glomeruli's functioning and cause their swelling and inflammation. As a result, large molecules like proteins escape into the urine instead of being reabsorbed into the blood circulation. Detection of these proteins in urine, as well as measuring levels of other kidney function markers and analysing a kidney biopsy tissue under an electron microscope, allows for a correct diagnosis to be made.

In the absence of a proper treatment for FGN, this condition is managed by using therapies that may help improve its symptoms and slow down the worsening of the disease.

Frequent and regular monitoring is essential in gauging whether these treatments are working or not and if kidney function is stable or improving. Patient education is always an important factor in achieving better health outcomes as it gives the patient more control over their health by understanding their condition and knowing what changes to implement and what to look out for.