Prurigo Nodularis and Cancer: What’s the Link?

Everyone’s had an itch they just needed to scratch. But in some cases, these itches are extreme and can lead to the development of large bumps called prurigo nodularis. 

Prurigo nodularis (PN) is a long-lasting itchy inflammatory skin disease. It shows up as circular bumps on the arms, legs, upper back, and abdomen. It can be scabby or scaly and flesh-colored, pink, red, black, or brown. There can be bleeding where the bumps have been scratched open. It has been linked to some cancers and cancer treatments.

Aside from unsightly bumps, PN can make life difficult by disrupting sleep and making it hard to work or enjoy recreational activities.

This article will explain prurigo nodularis and explore the link between prurigo nodularis and cancer.

The Link Between PN and Cancer

There are a few links between prurigo nodularis and cancer to explore. 

Some cases of PN appear when a person gets an underlying disorder that causes itching, stinging, or burning sensations. This underlying condition sometimes turns out to be cancer.

A study of 695 people with PN age 40 to 69 found that these cancers were most often skin cancer, blood cancer, gynecologic cancer, breast cancer, gastrointestinal cancer, or lung cancer. Of the 695 people in the study, 124 (18%) had a malignancy.

Cancers linked to PN include:

• Blood precancers (myelodysplasia,  monoclonal gammopathy of undetermined significance, or MGUS) 
• Blood cancers (leukemia, Hodgkin's lymphoma, non-Hodgkin's lymphoma, multiple myeloma, primary cutaneous lymphoma)
• Liver cancer
• Skin cancer
• Bladder cancer
• Lung cancer 
• Gastrointestinal cancers 
• Gynecologic cancers 

In addition, cancer treatments can cause itching, including chemotherapy and immunotherapy. In a study of 1,000 chemotherapy recipients, 384 developed skin issues. In the study, about 0.8% of the chemotherapy recipients (three total) developed PN.

PN has been associated with the chemotherapy drugs Taxol (paclitaxel) and Paraplatin (carboplatin). Studies have also linked PN to the immunotherapy drug Keytruda (pembrolizumab).

Cancer Screening of People With PN

If you have PN, it may be important to rule out certain underlying diseases that may be causing the itching and leading to the development of nodules. For this reason, your healthcare provider may suggest getting blood tests to determine if you have cancer or other diseases linked to PN.

Blood tests may include:

• Complete blood cell count (CDC)
• Complete metabolic panel (CMP)
• Thyroid, liver, and kidney function tests
• Test for human immunodeficiency virus (HIV) and hepatitis B and C

Depending on your medical history and physical examination, healthcare providers may also take a skin biopsy (removing a sample to be analyzed in the lab). They also may order imaging studies such as X-rays, computed tomography (CT), or magnetic resonance imaging (MRI).

Cancer Prevention

People with PN have a higher likelihood of having cancer. Because of the potential link between PN and cancer, all people with PN should ensure they’re getting the regular cancer screenings appropriate for their age, considering their other risk factors.

Prurigo Nodularis Causes

In many ways, PN is still a mystery. It can appear on its own or be associated with cancer or one of the many other diseases it has been linked to.  

Its cause is unknown. It seems to be linked to disruption of the immune system and possibly also the nerves that are in the skin. The nerves cause increased itchy sensations and lead to scratching and picking, which further causes the development of nodules on the skin.

The nodules are typically absent on areas of the skin like the back, where patients can’t reach—causing a butterfly pattern. 

Prurigo Nodularis Risk Factors

PN seems to occur more often in people who are:

• Older people
• Already have an inflammatory skin disease like eczema
• Are living with certain long-term diseases 

It is also possible that medications can lead to PN. Itchiness and PN have been reported as a reaction to chemotherapy agents paclitaxel and carboplatin and the immunotherapy drug Keytruda (pembrolizumab). These medications may lead to prolonged activation of the immune system that may lead to PN.

In the United States, studies estimate 72 new cases of PN for every 100,000 people between the ages of 18 and 64 years old. A study at the Johns Hopkins Health System found it was 3.4 times more common in Black Americans than in White Americans.

People with PN had an increased likelihood of:

• Eating disorders
• Self-harm
• Attention deficit hyperactivity disorder (ADHD) 
• Schizophrenia
• Mood disorders
• Anxiety
• Substance use disorders
• HIV infection
• Non-Hodgkin's lymphoma
• Eczema
• Psoriasis
• Obesity
• High blood pressure
• Type 2 diabetes
• Receiving dialysis
• Chronic kidney disease
• Heart failure
• Cerebrovascular disease 
• Coronary heart disease
• Chronic obstructive pulmonary disease (COPD)

These diseases are linked to an increased likelihood of having PN, but that doesn’t mean they cause PN. These conditions could lead to PN, but it could also be that mental and physical health declines in patients with PN. Or there could be no specific connection and the correlation could be due to outside factors. 

Treatment 

There are no specific treatments that have been approved by the Food and Drug Administration (FDA) to treat PN. Typically, healthcare providers will try treatments for other skin disorders on people with PN.

Other options include anti-inflammatory medications and those that can alter the immune response. These treatments don’t always work. Sometimes the discovery and treatment of an underlying condition will help clear up the itching and PN.

Some PN treatments that healthcare providers may try include:

• Oral antihistamines, like Claritin (loratadine), Benadryl (diphenhydramine), or Zyrtec (cetirizine)
• Corticosteroid creams applied to the skin
• Ceams containing immunosuppressants called calcineurin inhibitors or skin-numbing capsaicin
• Physical treatments, including cold therapy (cryotherapy) or light therapy (phototherapy)
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Injection of a steroid into the nodules
• Anti-itch lotions, including calamine, menthol, and camphor
• Narrow-band ultraviolet B (UVB) light treatment (performed in a dermatologist's office)

If medications can’t stop the itching, behavioral treatments may help reduce scratching. People with PN should:

• Keep their fingernails short
• Wear long sleeves and gloves
• Bandage their sores 
• Use gentle cleansers 
• Moisturize the skin with nonirritating lotions 
• Avoid warm environments to reduce sweating

Being itchy all the time can also mess with your mental health. Sometimes, healthcare providers will prescribe antidepressants; Neurontin (gabapentin), an antiseizure drug that also treats nerve pain; or sedatives to help with sleep and night-time itching.

Summary

Prurigo nodularis (PN) is a chronic inflammatory skin disease that causes itching and bumps across the arms, legs, and chest. Many times, there is an underlying disease that leads to itching. The underlying disease is sometimes cancer—the most common being blood cancers and skin cancers.

Cancer treatments can also lead to prurigo nodularis. People with PN should ask their healthcare provider if they need additional screenings to rule out underlying diseases. 

A Word From Verywell

Excessive itching can feel like it’s driving you mad. If you’re extremely itchy and are developing sores from it, see your healthcare provider for help, and get a second opinion if you are not satisfied. Ask the healthcare provider if they can screen you for underlying conditions that may be leading to your itching.