What is Poststreptococcal Glomerulonephritis?
Poststreptococcal glomerulonephritis, or PSGN in short, is a disease where your kidneys rapidly decline due to inflammation. This usually happens after an infection caused by certain types of streptococcal bacteria. These bacteria, known as nephrogenic streptococci, specifically target your kidneys. The disease primarily affects tiny blood vessels and structures in your kidneys called glomeruli.
PSGN most commonly emerges in children about 1 to 2 weeks after getting a sore throat or about 6 weeks after a skin infection. Though it’s become less common in developed countries, we see more cases from non-streptococcal bacteria. Bacteria produce harmful substances called Nephritis-associated plasmin receptor (NAPlr) and Streptococcal pyrogenic exotoxin B (SPeB). Not only do they cause a decrease in immune system components, but they also affect proteins in your kidneys. In some cases, people with PSGN may not have symptoms, while in others it can progress to kidney failure where dialysis is needed.
When symptoms do emerge, PSGN usually shows up with signs of nephritic syndrome like blood in the urine, urine reduction, high blood pressure, and swelling. Less commonly, it can mimic another condition, nephrotic syndrome, which includes significant protein loss in the urine.
What Causes Poststreptococcal Glomerulonephritis?
Post-Streptococcal Glomerulonephritis (PSGN), a kidney disease, often follows an infection typically affecting the skin or throat, caused by a type of bacteria called nephrogenic streptococci. Recently, it’s more often linked to skin infections like impetigo than throat infections like pharyngitis.
A specific type of bacteria, called Group A Streptococcus (GAS), is classified based on certain proteins on its surface. Some of these proteins are known to affect kidney functions and can cause PSGN. Yet, PSGN can also result from a variety of other infections. These include bacterial infections related to conditions like heart valve infection (endocarditis), bowel inflammation (enterocolitis), lung infection (pneumonia), infections caused by a device placed in the brain to manage fluid levels, and incidents of viruses (such as hepatitis B and C, HIV, cytomegalovirus, Epstein Barr virus, parvovirus B19). Fungal infections (like coccidioidomycosis, histoplasmosis) and parasitic infections (like malaria, leishmaniasis, toxoplasmosis, and schistosomiasis) are also potential causes.
Risk factors for outbreaks of streptococci, the bacteria that can lead to PSGN, include poor hygiene, crowded living conditions, and low socioeconomic status. This is why PSGN is more common in underprivileged countries. Genetic factors might also make a person more likely to develop PSGN, as about 40% of PSGN patients report a family history of the condition. However, no specific gene has been identified as the cause of PSGN yet.
Risk Factors and Frequency for Poststreptococcal Glomerulonephritis
Post-Streptococcal Glomerulonephritis (PSGN) is a kidney disorder that has decreased significantly in the US, UK, Central Europe, and Japan over the past 30 years. This reduction is thanks to the use of antibiotics and better hygiene. Despite this, it still remains the most common cause of kidney inflammation in children in the US.
PSGN is more frequently seen in adults with chronic illnesses in these developed countries. However, in developing countries, the condition is more prevalent due to increased skin infections. It is the leading cause of kidney injury in children in the Middle East, Africa, Australia and across the globe.
The incidence of new PSGN cases in developing countries ranges from 8.5 to 28.5 per 100,000 individuals each year. Interestingly, 97% of reported PSGN cases occur in less affluent countries.
- PSGN symptoms are usually more common in males, with a 2:1 ratio compared to females.
- However, non-symptomatic PSGN occurs almost equally in males and females.
- Race doesn’t seem to influence the occurrence of this disease.
- The disease primarily affects children aged between 3 and 12 years old, with a peak incidence between 5 to 6 years.
- It also affects seniors over 60 years old.
Signs and Symptoms of Poststreptococcal Glomerulonephritis
Post-streptococcal glomerulonephritis, or PSGN, often occurs following a streptococcal infection, such as a throat infection or a skin infection. It’s a kidney disease where half of the children affected are asymptomatic, meaning they don’t show any symptoms and are only diagnosed during routine urine tests. It’s important to note that some people might have PSGN without ever having experienced obvious symptoms of a prior infection, which can make diagnosis tricky.
- Blood in the urine: The most common symptom, occurring in 30-50% of cases. The urine might appear smoky, the color of tea, cola, or rusty. This is typically noticeable a few weeks following an infection.
- Kidney issues: These happen frequently but usually get better within 1-2 weeks. Some patients may have low urine output.
- Life-threatening complications: Depending on the severity of the kidney involvement, complications may arise, including poor kidney function (anuric renal failure), severe acid-base imbalance, and dangerous electrolyte abnormalities such as high potassium (hyperkalemia), requiring renal replacement therapy (RRT).
- High blood pressure: Seen in 60-80% of cases and usually resolves within 10 days.
- Swelling: Occurs in 65-90% of patients. The puffiness is typically seen around the eyes, especially in the morning, and lessens towards the end of the day. Widespread body swelling may also occur. In severe cases, fluid can accumulate in the lungs, leading to breathing difficulties.
- Other symptoms: These may include loss of appetite, nausea, vomiting, and a general feeling of discomfort or illness.
Testing for Poststreptococcal Glomerulonephritis
If a child has high blood pressure and heart failure, there might be a chance that they have a condition known as PSGN. This suspicion can arise even if there are no signs of blood in the urine or previous experiences with a sore throat or a type of skin infection known as pyoderma.
To check for PSGN doctors often order laboratory tests. Specifically, they look for signs of a recent infection caused by streptococcus bacteria. Signs of this sort of infection can be seen by measuring the levels of certain antibodies in the blood, which tend to increase following a throat infection. Antibodies such as anti-streptolysin (ASO), anti-nicotinamide-adenine dinucleotidase (anti-NAD), anti-DNAse B, and anti-hyaluronidase (AHase) might be present. Of these, ASO is the most common, while the streptozyme test, which measures all the antibodies, is the most detailed and sensitive. However, be aware that if you were treated with antibiotics for a streptococcus infection, your ASO levels might be falsely low.
Another signal of PSGN is low levels of complement protein (C3) in your blood, as a lot of this protein is needed for the body’s inflammatory response to the streptococcus bacteria. Usually, C3 levels drop before ASO levels go up, and they tend to return to normal in about 6-8 weeks.
To investigate further, doctors might check your urine, as PSGN can cause blood cells to appear in the urine, and sometimes small amounts of protein. Note that only about 5% of those with PSGN have massive protein in their urine, signalling a condition known as nephrotic syndrome. They might also see other types of cells that are usually found in the urine under these circumstances.
Doctors might also check your kidney function by measuring Blood Urea Nitrogen (BUN) and serum creatinine in the blood, which typically go up during PSGN and return to normal afterwards.
If you have symptoms of heart failure along with PSGN, a protein called NT-proBNP in your blood might be high and a chest X-ray might show fluid in your lungs.
While a kidney biopsy might sound like a useful way to check for PSGN, it is generally not recommended unless other kidney diseases are suspected. Doctors might prefer a kidney biopsy if your kidney function is declining markedly, if you stop producing urine, if symptoms of PSGN appear suddenly with no previous streptococcal infection, if complement levels are normal or if ASO levels are not rising.
In terms of imaging, doctors might order ultrasound scans, although this will only show enlarged kidneys in a few patients. A chest x-ray might be needed if you have symptoms suggesting that your heart is having trouble pumping fluids around your body; this could indicate fluid building up in your lungs.
Treatment Options for Poststreptococcal Glomerulonephritis
Poststreptococcal glomerulonephritis (PSGN) is a condition that often gets better on its own. The focus of the treatment is to manage the complications like high blood pressure and swelling, which are common during the early stages of the disease.
Antibiotics are given if there are signs of a strep infection, but they might not prevent PSGN from developing.
To reduce excess fluid in the body and manage high blood pressure, diuretics are used – these are medicines that help your body get rid of extra fluid. Of the two kinds of diuretics – loop and thiazide – the former (commonly furosemide) is usually preferred. Thiazide diuretics (like hydrochlorothiazide or chlorthalidone) are less effective when your kidneys are not functioning optimally (glomerular filtration rate or GFR less than 30 ml/min.)
Reducing the intake of salt and fluid can also help with managing blood pressure. In instances where blood pressure is not controlled even after taking diuretics, calcium channel blockers may be prescried by doctors. Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARBs) are recommended for patients with stable kidney function and near-normal potassium levels.
Immunosuppressive therapy – medicines given to dampen the body’s immune response – does not have enough evidence to support its usefulness in patients with PSGN. However, patients with rapidly worsening kidney function or specific findings on a kidney biopsy may be treated with corticosteroids which reduce inflammation.
In certain cases, dialysis may be performed. Dialysis is a procedure that purifies the blood and is done in cases where the body has trouble maintaining a stable internal environment. It helps manage the acid-base balance, corrects abnormal electrolyte levels (particularly high potassium), and manages fluid levels in the body.
General measures include reducing the intake of salt and water to treat swelling. Resting and staying immobile are suggested in the initial days of the disease. Throat cultures are recommended to identify those with a strep infection – these are tests that check the throat for germs. It’s important to give antibiotics to everyone who is affected, and penicillin or erythromycin are typically used.
What else can Poststreptococcal Glomerulonephritis be?
There are several conditions that share similar symptoms to nephrotic syndrome, including:
- IgA Nephropathy: This usually shows up after an upper respiratory tract or gastrointestinal infection. Unlike some other conditions, it occurs shortly after infection. Sometimes, the infection and hematuria, or blood in the urine, happen at the same time.
- Membranoproliferative glomerulonephritis: This may also appear after a respiratory tract infection. It features low complement protein levels which take longer to come back to normal than in some other conditions.
- Lupus nephritis: Sometimes, this disease presents in a similar way to nephrotic syndrome. Lab tests for specific antibodies can help identify Lupus nephritis. Indicators include positive ANA, ds-DNA, cytopenia, and issues affecting multiple organs.
Nephrotic syndrome itself is diagnosed when a person’s 24-hour urine protein excretion is more than 3.5 grams per day. Other symptoms and signs can include low albumin levels, swelling, reduced levels of immunoglobulins, and an increased risk of blood clots. Here are some other conditions to consider:
- Henoch Schonlein purpura (HSP): Common symptoms include palpable purpura, which are raised purple spots on the skin, kidney failure, gastrointestinal symptoms, and musculoskeletal issues. Complement protein levels will be normal in this case.
- Hemolytic uremic syndrome (HUS): Tests reveal hemolysis or breakdown of red blood cells, bloody diarrhea, low platelet count, and the presence of harmful Escherichia coli bacteria. Again, complement protein levels would be normal.
- Goodpasture Disease: Affects both lungs and kidneys. Patients usually test positive for the anti-glomerular basement antibody and maintain normal complement levels.
What to expect with Poststreptococcal Glomerulonephritis
PSGN (Poststreptococcal Glomerulonephritis, a type of kidney disease) generally has a good outcome, particularly in children. Complete recovery usually happens within 6 to 8 weeks. In adults, however, about half of the patients may continue to experience reduced kidney function, high blood pressure, or persistent proteinuria (excessive protein in the urine).
In adults, death often occurs due to heart failure and kidney dysfunction. Some research suggests that in the long run, some patients may continue to experience abnormalities in their urine, proteinuria (too much protein in the urine), and hypertension (high blood pressure).
The death rate during the acute (initial) phase of glomerulonephritis (a type of kidney inflammation) is estimated to be between 2 and 12 percent. It’s thought that the changes in the kidneys in the majority of patients who survive the initial acute attack would be similar to those seen in fatal cases, although there’s not much direct evidence to support this idea.
Possible Complications When Diagnosed with Poststreptococcal Glomerulonephritis
In the initial phase of illness, serious complications such as congestive heart failure and azotemia (an excess of nitrogenous waste products in the blood) can occur and may be potentially life-threatening. Over the long term, complications like chronic kidney disease (long-term damage to the kidneys) and nephrotic syndrome (a kidney disorder causing the body to excrete too much protein in the urine) could happen.
Possible Complications:
- Congestive heart failure
- Azotemia
- Chronic kidney disease
- Nephrotic syndrome
Preventing Poststreptococcal Glomerulonephritis
It’s important for individuals to avoid crowded conditions and maintain personal cleanliness to lower their risk of contracting streptococcal infections, which can cause various illnesses like strep throat or skin infections.
If people experience symptoms like a sore throat or skin infection, they should reach out to a healthcare provider and ensure they undergo suitable antibiotic treatment if they’re diagnosed with a bacterial infection.
