Prurigo nodularis (PN), or nodular prurigo, is an inflammatory skin disorder that is often associated with other health conditions that lead to pruritus (itching). Frequent scratching can cause PN nodules to form, leading to even more itching. This process is known as the itch-scratch cycle. Treating other itch-causing medical conditions can be an important part of managing PN.

If you have PN and other health and skin conditions alongside PN, you may require additional types of treatment. Here we’ll discuss 11 conditions or groups of conditions related to prurigo nodularis and how they’re related to the skin disorder.

Prurigo Nodularis Comorbidities

When someone has two or more health conditions at the same time, the conditions are known as comorbidities. Studies have found that between 7 to 9 out of 10 people with PN have comorbidities alongside PN.

1. Skin Conditions

A study in the journal Acta Dermato-Venereologica showed that in half of the cases, PN develops in people with another skin disease. Per the American Academy of Dermatology Association, people with the following conditions have a higher risk of developing PN:

• Atopic dermatitis (eczema) — Skin inflammation leading to dry, thickened, itchy skin
• Contact dermatitis — A rash caused by coming into contact with something that causes irritation or triggers allergies (such as poison ivy)
• Lichen planus — An immune system reaction that causes flat, itchy bumps on the skin

Treating these conditions and keeping itching under control may help you avoid developing PN and PN symptoms.

PN can also occur at the same time as other skin conditions. In some cases, people may be incorrectly diagnosed with one of these conditions rather than PN because they all have similar symptoms. Some of these related skin disorders include:

• Pemphigoid nodularis — A rare type of bullous pemphigoid (a blistering disease in which the immune system attacks itself) with nodular prurigo-like lesions and pemphigoid blisters
• Lichen simplex chronicus — A condition that starts with an itchy patch of skin with dry areas that are scaly and thick
• Lupus erythematosus — An ongoing disease in which the immune system attacks its own tissues
• Psoriasis vulgaris — An inflammatory skin condition wherein skin cells build up and form scales and itchy, dry, raised patches of skin

Tests like skin biopsies allow doctors to study a piece of skin more closely to tell these different conditions apart.

2. Allergies

Some people have gene changes that make them more likely to have allergies or other related conditions like asthma and hay fever. All of these conditions have been linked to an overactive immune system, which is one of the possible causes of PN. Those who have allergies or asthma may be more likely to develop PN.

3. Infections

Certain infections can cause itching that leads to PN. Viral infections that increase PN risk include hepatitis C, herpes zoster, and untreated HIV. Some bacterial infections like tuberculosis and H. pylori can also cause PN. Finally, PN can sometimes be caused by parasitic infections like strongyloidiasis or ascariasis.

If your doctor diagnoses you with PN, they may also recommend tests to check for an infection or other condition.

4. Heart and Lung Diseases

People with PN are more likely to have conditions that affect the heart and lungs. Heart problems linked to PN include hypertension (high blood pressure), ischemic heart disease (narrowing or hardening of the arteries), and heart failure (when the heart can’t pump enough blood).

Chronic obstructive pulmonary disease (COPD), an inflammation of the lungs or airways, has also been found to be associated with PN.

5. Cancers

Some people develop PN as a result of cancer or its treatments. Cancers that affect blood cells are one possible cause. These include:

• Lymphoma, including Hodgkin lymphoma, non-Hodgkin lymphoma, and cutaneous T-cell lymphoma
• Leukemia, including a type of leukemia called polycythemia vera
• Multiple myeloma
• Myelodysplastic syndrome

Precancerous blood conditions can also lead to PN. One such condition, monoclonal gammopathy of undetermined significance (MGUS), is a noncancerous condition that can lead to multiple myeloma.

PN may also be caused by other types of cancer, such as skin cancer, lung cancer, cancer of the intestines or colon, liver cancer, breast cancer, head and neck cancer, bladder cancer, and reproductive cancers such as vaginal cancer.

Drugs to treat cancer, such as carboplatin (Paraplatin), paclitaxel (Taxol), and pembrolizumab (Keytruda), can also increase the risk of PN.

6. Neurological Conditions

The nervous system, including the brain, spinal cord, and nerves, also seems to play a role in PN. In some cases, nerve changes or damage may cause itching and make PN more likely to develop. Herpes infections, shingles infections, itching after a burn, and neuropathies (problems with nerves that lead to tingling, numbness, or pain) can all cause this type of damage that leads to intense itching. The scratching itself may affect the nerves.

7. Other Comorbidities

PN has also been linked to a variety of other conditions:

• Diabetes
• Gout (a type of arthritis in which the immune system attacks the joints)
• Anemia (low red blood cell levels)
• Kidney disease
• Liver disease
• Thyroid conditions
• Overactive parathyroid glands
• An overactive pituitary gland
• Amyloidosis (a condition when abnormal proteins build up in the body)
• Celiac disease (a condition in which the intestines become damaged after eating gluten)

If you don’t know what is causing your PN, you may need tests to look for underlying health problems. Basic blood tests can show how well your kidneys, liver, and thyroid are working and determine whether you might have a condition like diabetes. Additional tests may be needed if your doctor thinks you might have another disorder. In many cases, no underlying cause of PN is identified.

8. Psychological Conditions

In some cases, conditions like anxiety, depression, and dissociative disorders can be associated with intense itching that causes PN.

Prurigo Nodularis Complications

When someone develops a medical problem in addition to or because of another condition, it is known as a complication. PN can cause complications. Treating PN may help improve these conditions or make them easier to deal with.

9. Infected Nodules

Scratching too much can cause skin lesions (abnormal skin changes) to break open, which allows germs to enter the skin. This can lead to an infection, which may require more treatment options such as topical and oral antibiotics.

10. Sleeping Difficulties

People with PN may have more severe itching symptoms at night, which can make it hard to fall or stay asleep. This may lead to sleeping problems and tiredness during the day.

In one study from the journal Acta Dermato-Venereologica, 7 out of 10 people with PN said that their condition got in the way of their sleep to a moderate or large extent. Treating PN and reducing itching often helps people sleep better.

11. Mental Health Changes

PN can also affect your mental health. Some people with the condition may feel differently about their skin and body image. Symptoms of PN occasionally cause people to miss work, school, or social activities. Some may have a harder time following their usual daily routines. This often happens when a person is not sleeping well at night.

These and other factors can play a role in developing mental health conditions like depression or anxiety. One study found that nearly half of people with PN currently or previously had a mental health condition.

Talk to your healthcare team if you notice any mood or behavior changes, or if you find yourself avoiding things you used to enjoy. Various treatments, including antidepressants and counseling, can help with mental health changes and improve your mental well-being.

The Impact of Comorbidities and Complications

Having comorbidities and complications may make it harder to deal with PN. Especially if you experience symptoms from a comorbidity along with PN symptoms, such as severe itching.

Work with your primary and dermatology healthcare teams to make sure you get treatment for any underlying medical issues. Managing these other conditions may help treat your PN, prevent new nodules from forming, and improve your quality of life.

Find Your Team

On MyPrurigoTeam, people talk about their experiences with prurigo nodularis, get advice, and find support from others who understand.

Do you have prurigo nodularis? Have you had any complications because of it? Share your story in the comments below.