Fibronectin glomerulopathy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Fibronectin glomerulopathy is a kidney disease that usually develops between early and mid-adulthood but can occur at any age. It eventually leads to irreversible kidney failure (end-stage renal disease).

Individuals with fibronectin glomerulopathy usually have blood and excess protein in their urine (hematuria and proteinuria, respectively). They also have high blood pressure (hypertension). Some affected individuals develop renal tubular acidosis, which occurs when the kidneys are unable to remove enough acid from the body and the blood becomes too acidic.

The kidneys of people with fibronectin glomerulopathy have large deposits of the protein fibronectin-1 in structures called glomeruli. These structures are clusters of tiny blood vessels in the kidneys that filter waste products from blood. The waste products are then released in urine. The fibronectin-1 deposits impair the glomeruli's filtration ability.

Fifteen to 20 years following the appearance of signs and symptoms, individuals with fibronectin glomerulopathy often develop end-stage renal disease. Affected individuals may receive treatment in the form of a kidney transplant; in some cases, fibronectin glomerulopathy comes back (recurs) following transplantation.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Fibronectin glomerulopathy can be caused by mutations in the FN1 gene. The FN1 gene provides instructions for making the fibronectin-1 protein. Fibronectin-1 is involved in the continual formation of the extracellular matrix, which is an intricate lattice of proteins and other molecules that forms in the spaces between cells. During extracellular matrix formation, fibronectin-1 helps individual cells expand (spread) and move (migrate) to cover more space, and it also influences cell shape and maturation (differentiation).

FN1 gene mutations lead to production of an abnormal fibronectin-1 protein that gets deposited in the glomeruli of the kidneys, probably as the body attempts to filter it out as waste. Even though there is an abundance of fibronectin-1 in the glomeruli, the extracellular matrix that supports the blood vessels is weak because the altered fibronectin-1 cannot assist in the matrix's continual formation. Without a strong cellular support network, the glomeruli are less able to filter waste. As a result, products that normally are retained by the body, such as protein and blood, get released in the urine, and acids are not properly filtered from the blood. Over time, the kidneys' ability to filter waste decreases until the kidneys can no longer function, resulting in end-stage renal disease.

It is estimated that mutations in the FN1 gene are responsible for 40 percent of cases of fibronectin glomerulopathy. The cause of the remaining cases of this condition is unknown.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

When fibronectin glomerulopathy is caused by mutations in the FN1 gene, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In some of these cases, an affected person inherits the mutation from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family. Some people who have the altered FN1 gene never develop the condition, a situation known as reduced penetrance.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Fibronectin glomerulopathy is likely a rare condition, although its prevalence is unknown. At least 45 cases have been described in the scientific literature.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Glomerulopathy · Very frequent (99-80%)

Inflammatory or noninflammatory diseases affecting the glomeruli of the nephron.

Hypertension · Very frequent (99-80%)

The presence of chronic increased pressure in the systemic arterial system.

Hypoalbuminemia · Very frequent (99-80%)

The concentration of albumin in the blood circulation is below the lower limit of normal.

Mesangial abnormality · Very frequent (99-80%)

An abnormality of the mesangium, i.e., of the central part of the renal glomerulus between capillaries.

Microscopic hematuria · Very frequent (99-80%)

Microscopic hematuria detected by dipstick or microscopic examination of the urine.

Nephrotic syndrome · Very frequent (99-80%)

Nephrotic syndrome is a collection of findings resulting from glomerular dysfunction with an increase in glomerular capillary wall permeability associated with pronounced proteinuria. Nephrotic syndrome refers to the constellation of clinical findings that result from severe renal loss of protein, with Proteinuria and hypoalbuminemia, edema, and hyperlipidemia.

Pedal edema · Very frequent (99-80%)

An abnormal accumulation of excess fluid in the lower extremity resulting in swelling of the feet and extending upward to the lower leg.

Proteinuria · Very frequent (99-80%)

Increased levels of protein in the urine.

Other findings in the same source

From: Orphanet

Additional reported features include Renal insufficiency (Very frequent (99-80%)); Cerebral hemorrhage (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Fibronectin glomerulopathy is Nephrology, with a nephrologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• How is kidney function being assessed over time?
• Are any current medicines or supplements relevant to kidney safety?
• Is there an individual recommendation about fluids, diet or blood pressure?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.