Although psoriasis primarily affects the skin, it can also affect other parts of the body, including your white blood cell (WBC) count. WBCs play an important role in how your immune system fights off disease, and when your WBC levels are out of balance, you may be prone to getting sick more often or developing other symptoms.

Beyond psoriasis, other factors can lead to abnormal WBC count, including psoriasis treatments or unrelated health conditions. If your doctor determines through a blood test that your WBC count is off, they can work with you to find ways to treat it and help you feel better.

What Are White Blood Cells?

WBCs — also called leukocytes — are immune system cells that circulate through your blood and help your body respond to injury or infections.

There are five main types of WBCs:

• Neutrophils primarily protect you from infections and heal damaged tissues.
• Lymphocytes, which include T cells and B cells, protect you from infections and make proteins called antibodies that help recognize foreign invaders.
• Basophils are responsible for producing an allergic response.
• Eosinophils protect you from parasites, cancer cells, and help produce an allergic response.
• Monocytes help get rid of damaged or infected cells.

Measuring WBCs

Your doctor can check your WBC count with a blood test called a complete blood count (CBC). Usually, a CBC measures only your total WBC, but if your doctor orders a differential, your CBC results will include a count of each type of WBC present in your blood.

A CBC may determine you have leukocytosis, which means a high WBC count. Leukocytosis can be a sign of inflammation, and it has several potential causes, including:

• Infection
• Allergies
• Excess stress
• Thyroid issues
• Immune disorders, such as rheumatoid arthritis or lupus
• Some medications, such as corticosteroids

A CBC may also reveal that you have leukopenia, which means low levels of WBCs. Usually, leukopenia refers specifically to a lower-than-normal number of neutrophils. It may be caused by:

• Autoimmune disorders
• Bone marrow disorders, such as multiple myeloma
• Infection, such as human immunodeficiency virus (HIV)
• Certain medications
• Vitamin deficiency and/or malnutrition

If you have leukopenia, you may have an increased risk of infections.

How Can Psoriasis Affect WBCs?

Normally, WBCs circulate around your body in your blood and search for things that shouldn’t be there. This includes foreign invaders (bacteria, viruses, and fungi) and damaged cells (old cells and cancer cells). When WBCs find something abnormal, they try to get rid of it to keep you healthy.

In autoimmune disorders like psoriasis, WBCs mistakenly recognize healthy cells as foreign invaders and attack them. In psoriasis, your WBCs — primarily your T cells — attack your skin cells, causing inflammation and skin symptoms. The T cells release inflammatory chemicals called cytokines that recruit (send signals to gather) other WBCs, especially neutrophils, to the area. Neutrophils also release cytokines and other signaling proteins responsible for inflammation in psoriasis.

High White Blood Cell Count

Inflammation can cause your body to produce too many WBCs. Given that psoriasis flare-ups involve inflammation, it makes sense that people with the condition often have leukocytosis. Researchers have found that levels of neutrophils in particular are commonly higher in people with psoriasis.

In rare cases, a high WBC count can be a sign of cancer, such as lymphoma. People with psoriasis have a slightly increased risk of developing cancer, particularly lymphoma and keratinocyte cancer. The risks may be higher among people with severe psoriasis compared to those with mild psoriasis. Scientists aren’t sure why people with psoriasis are at a higher risk of lymphoma, but it could be related to chronic (ongoing) immune system activation.

Low White Blood Cell Count

Researchers have found that people with psoriasis may have decreased levels of lymphocytes, especially T cells. Scientists don’t know why exactly this happens, but it could be related to T-cell involvement in causing inflammation.

Neutrophil-to-Lymphocyte Ratio

Your doctor may use the results of your WBC count to calculate a neutrophil-to-lymphocyte ratio (NLR). Studies have found this ratio is commonly higher in people with psoriasis. Researchers are currently investigating whether the NLR could help diagnose different types of psoriasis and assess how well your psoriasis treatment is working.

Can Psoriasis Medications Affect WBC Counts?

The side effects of some oral treatments and biologics used to treat psoriasis and psoriatic arthritis (PsA) can also affect WBC counts. Your dermatologist will monitor you for abnormal WBC counts while you are taking medication to treat psoriasis.

Oral Treatments and WBCs

Psoriasis oral treatments are small-molecule drugs that target your immune system to decrease inflammation caused by psoriasis. These medications can affect your WBC count by suppressing your immune system.

Up to 25 percent of people taking acitretin (Soriatane) experience either an increase or decrease in their WBC count. Other oral treatments like cyclosporine (Neoral) and methotrexate (Trexall) also include leukopenia as a possible side effect.

Biologic Treatments and WBCs

Biologic treatments are protein-based drugs given by an injection into the skin or vein that target specific parts of the immune system. Biologics for the treatment of psoriasis are also associated with a decrease in WBC count, especially a decrease in neutrophils.

Secukinumab (Cosentyx) specifically targets interleukin-17 (IL-17), which is primarily produced by neutrophils. A 2021 study found that secukinumab decreased both neutrophil counts and leukocyte counts in people with psoriasis. Researchers have also seen this effect with ustekinumab (Stelara), an IL-12 and IL-23 inhibitor.

Tumor necrosis factor-alpha (TNF-alpha) inhibitors such as adalimumab (Humira) and IL-23 inhibitors such as risankizumab-rzaa (Skyrizi) are also associated with low neutrophil counts.

Although biologic medications are most commonly associated with a decrease in WBC count, they may increase WBCs in the case of lymphoma. Past research suggested that TNF-alpha inhibitors and other biologic medications could be associated with an increased risk of lymphoma and other cancers. However, newer research suggests this may not be true and that uncontrolled inflammation from psoriasis may be the cause of the increased cancer risk.

All medications, even those sold over the counter, carry the risk of potential side effects. Your doctor is the best person to help you understand your risks and weigh the potential benefits versus the potential side effects of each treatment option.

Symptoms of High or Low WBC Count

Talk to your doctor or dermatologist about how often you should have a CBC blood test to check your WBC count. The frequency may be different depending on the severity of your psoriasis, which medications you are taking, and your symptoms.

Not everyone with a high or low WBC count will have symptoms. Symptoms of either a high or low WBC count can include:

• Fever
• Wounds that don’t heal
• Frequently illness
• Unexplained cough that doesn’t go away
• Easy bruising
• Mouth sores

Because some of these symptoms are so general and may indicate an infection or other issues, it can be difficult to tell if they’re related to changes in WBC. If you’re concerned about any of these symptoms, talk to your doctor. A blood test is the only way to determine if you have an abnormal WBC count.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriasis and their loved ones. On MyPsoriasisTeam, more than 116,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

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