The Association Between Psoriatic Arthritis and Kidney Disease: What to Know

Inflammation caused by psoriatic arthritis (PsA) can increase your risk for additional diseases (comorbidities), like heart disease, hypertension, and stroke. Research from 2017 found that having psoriatic arthritis also can increase your risk of kidney disease.

In this article, we'll discuss the connection between psoriatic arthritis and kidney disease, as well as the causes, prevention, and treatment methods.

What Is Psoriatic Arthritis?

Psoriatic arthritis is an inflammatory type of arthritis that develops in some people with psoriasis, an autoimmune disease that causes itchy, scaly plaques on the skin. Psoriasis affects 74 million adults in the United States, and 30% of patients diagnosed with psoriasis will develop psoriatic arthritis.

PsA causes inflammation in many joints of the body as a result of the body producing autoantibodies (proteins of the immune system) that attack healthy joints by mistake. This results in joint pain, inflammation, and stiffness, in addition to symptoms of the skin for some. 

Psoriasis and Your Risk for Other Conditions

As an autoimmune inflammatory condition, psoriasis shares a link with other systemic conditions like diabetes, metabolic syndrome, heart disease, stroke, and high blood pressure based on a shared underlying cause.

It is believed that these conditions result from chronic inflammation throughout the body caused by the activation of T-cells, a type of white blood cell involved in immune system responses, and specific cytokines (inflammatory proteins).

The Link Between Psoriatic Arthritis and Kidney Disease

Markers of normal kidney functioning include:

• Serum creatinine levels in the blood, a waste product of muscular activity
• Urea, a waste product produced by your liver from the digestion of protein
• Phosphate, an electrolyte

Normally, the kidneys filter out these substances from the blood to maintain levels within a healthy range.

When the kidneys don't function properly, serum creatinine, urea, and phosphate will stay in the blood and cause higher-than-normal levels, which indicate kidney disease or malfunctioning. Elevated levels of protein in the blood are also commonly seen when the kidneys are not functioning properly. 

The level of serum creatinine in your blood as well as your age, gender, and race all factor in to your glomerular filtration rate, which is another marker of healthy kidney functioning. If serum creatinine levels are elevated, your glomerular filtration rate will be lower since the kidneys are not effectively filtering out creatinine from the blood. 

A 2017 epidemiological study examined markers of kidney function among patients with psoriatic arthritis, patients with psoriasis, and healthy control subjects. This study revealed that levels of serum creatinine, urea, and phosphate were all elevated in patients with psoriasis compared to healthy subjects, but levels were highest among the patients with psoriatic arthritis.

Additionally, the glomerular filtration rate was measured in all participants of the study and was found to be lowest among the patients with psoriatic arthritis. It was also lower in patients with psoriasis compared to the average rate of healthy subjects.

Proteinuria, or elevated levels of protein in the blood, was also found in 96.7% of patients with psoriatic arthritis but only in 10% of patients with psoriasis. Kidney biopsies were taken of the patients with proteinuria and most revealed membranous glomerulonephritis, which is inflammation of the glomeruli, or small capillaries, of the kidneys that filter the blood. Glomerulonephritis is one of the three major causes of chronic kidney disease.

Symptoms of Psoriatic Arthritis and Kidney Disease

Psoriatic arthritis sometimes develops in patients with psoriasis, an autoimmune skin condition that causes red, itchy, scaly, and inflamed plaques on the skin. Psoriatic arthritis is characterized by joint pain, inflammation, and stiffness.

The widespread inflammation that affects the skin and joints in psoriatic arthritis can also extend to other areas of the body, causing:

• Nail changes
• Swollen fingers or toes with a sausage-like appearance (dactylitis)
• Inflammation of the eyes (uveitis)
• Inflammation of the sites where tendons and ligaments attach to bone (enthesitis)

Other systemic symptoms can include chronic fatigue, digestive symptoms, such as abdominal pain, bloating, constipation, and diarrhea, and organ damage from inflammation of the heart, lungs, or kidneys.

With kidney disease, because toxic byproducts are not effectively being filtered out of the blood, increased inflammation throughout the body can manifest in several ways, including:

• Fatigue
• Trouble concentrating
• Difficulty sleeping
• Increased urge to urinate
• Dry and itchy skin
• Muscle cramping
• Swollen joints
• Abnormal urine, either bloody or foamy, from blood vessel damage or increased protein content

Diagnosis and Treatment

A combination of a physical exam, a review of your medical history, your symptoms, and X-ray imaging will be used to confirm a diagnosis of psoriatic arthritis and identify the affected joints. 

Blood tests that examine your erythrocyte sedimentation rate (ESR) and levels of C-reactive protein can help confirm a diagnosis of psoriatic arthritis since these markers are typically elevated with this condition. Blood tests are also crucial for measuring your levels of serum creatinine, urea, phosphate, and glomerular filtration rate to diagnose kidney disease. 

A urinalysis to examine the levels of protein in a sample of your urine can also help your doctor diagnose kidney disease. If blood work and urinalysis come back abnormal, an ultrasound or computed tomography (CT) scan may be performed to examine the appearance of your kidneys to check for signs of damage. 

Prescription medication, such as disease-modifying antirheumatic drugs (DMARDs) like methotrexate and biologics like TNF-inhibitors like etanercept, are often prescribed to decrease inflammation in autoimmune conditions like psoriasis and psoriatic arthritis. These medications help reduce numbers of inflammatory T-cells and reduce levels of inflammatory cytokines, which can also decrease symptoms of kidney disease.

Ways to Prevent Damage to Your Kidneys

To help keep your kidneys healthy, proper management of any underlying conditions decreases your risk of developing kidney disease.

Healthy lifestyle habits can also help you manage these conditions and reduce inflammation throughout the body to prevent kidney damage. Healthy lifestyle habits include:

• Getting enough sleep at night, at least seven to eight hours
• Eating a healthy diet and maintaining a healthy weight
• Quitting smoking
• Limiting alcohol consumption
• Staying adequately hydrated
• Maintaining a positive attitude and learning how to cope with and manage stress
• Exercising regularly and staying active

Summary

The inflammation caused by PsA can potentially affect your kidneys and lead to kidney disease. This is because PsA can cause inflammation throughout the body. Similarly, having the autoimmune skin condition psoriasis also increases your risk of having other conditions like heart disease and stroke.

Research has shown that people with psoriatic arthritis may be more likely to have glomerulonephritis, which is inflammation of the small capillaries of the kidneys that filter the blood. This condition is linked to chronic kidney disease.