What is Prurigo Nodularis : Symptoms, Causes, Treatment, Prevention

Prurigo nodularis is a type of extremely itchy skin rash. Prurigo nodularis causes bumps on the skin that varies in size from being tiny to nearly a half inch in diameter. The condition causes a rash that includes the appearance of hard lumps known as nodules. Due to this, the condition is sometimes also called nodular prurigo. Here is a complete guide to this rare disease known as prurigo nodularis.

Prurigo nodularis (PN) is a condition that causes an extremely itchy skin rash. The condition often causes hard lumps to develop that are known as nodules. Due to this, Prurigo nodularis is sometimes also known as nodular prurigo. While the exact cause of Prurigo nodularis is not known, but what is known is that the condition is not contagious.

Prurigo nodularis mostly affects people who are middle-aged and it is also more common in people who are Black.^(1, 2, 3)

Prurigo nodularis is most commonly observed in people between the ages of 20 to 60 years, and it affects both men and women equally. This is a rare condition and there are only a few studies that mention the prevalence or incidence of this illness. In 2018, a study carried out on 909 patients with prurigo nodularis found that African American patients were 3.4 times more likely to develop this condition as compared to white patients.^(4, 5, 6)

The number of Prurigo nodularis bumps varies from person to person and usually ranges from 2 to 200. The size also varies from being very small to around half an inch in diameter. It is commonly believed that prurigo nodularis develops from scratching the skin too harshly. However, itchy skin usually happens due to a variety of reasons, including:

• Dry skin
• Chronic kidney disease
• Thyroid dysfunction

The itching of the skin caused by Prurigo nodularis is usually debilitating because of its severity. In fact, prurigo nodularis is believed to have the highest itch intensity of any other type of itchy skin condition. Scratching, though, only makes the itching worse and it can actually cause even more bumps to appear, as well as worsen the existing bumps. Prurigo nodularis is a rare condition that is a challenge to treat.

Prurigo nodularis usually begins as a small, red itchy bump or nodule that develops due to the scratching of the skin. The bumps then start to appear on your arms or legs. These bumps may also develop on the rest of the body, depending on where you scratch. These nodules are extremely itchy and they may also be:

• Crusty and scaly
• Hard to touch
• Scabby
• Look like a wart
• Differ in color from being flesh tones to brown, black, or pink

The skin present between the bumps tends to be dry. Some people with this condition may also experience stinging, burning, as well as variations in temperature in the bumps.^(7, 8, 9)

If you frequently keep on scratching the bumps, it might lead to secondary infections as well. The extreme itching associated with prurigo nodularis can be debilitating for the person. It may prevent you from sleeping properly at night and also disrupt your day-to-day routine. This, in turn, often causes people with Prurigo nodularis to feel depressed and distressed over their condition.

The good news is that the bumps may resolve on their own if you stop scratching them, though in some cases, the bumps may leave behind scars.

The exact cause of prurigo nodularis is not clearly understood. However, the bumps that occur are believed to be because of the itchy skin, which can be caused due to several reasons. Prurigo nodularis is believed to be associated with many other health conditions, such as:

• Congestive heart failure
• Diabetes
• Chronic kidney failure
• Chronic hepatitis C
• Atopic dermatitis (eczema)
• Lymphoma
• Lichen Planus
• Psychiatric disorders
• Neurological disorders
• HIV
• Chronic obstructive pulmonary disease (COPD)

Some therapeutic drugs used in cancer treatment (for example carboplatin, paclitaxel, and pembrolizumab)

It is believed that prurigo nodularis develops when other medical conditions start causing persistent scratching and itching, known as the itch-scratch cycle and results in the formation of the characteristic nodules. Even after the underlying condition is treated, prurigo nodularis can still continue to persist.^(10, 11)

A study hailing from 209 found that nearly 13 percent of people who develop Prurigo nodularis do not have any underlying or predisposing illness or other factors responsible for causing the condition.⁽⁷⁾ Researchers are still continuing to find out about the exact underlying mechanisms involved in causing Prurigo nodularis, including:

• Nerve fibers
• Changes in skin cells
• Changes in the neuroimmune system and neuropeptides

It is expected that as new research makes the cause of prurigo nodularis clearer, better treatments can be developed for the condition.

The focus of prurigo nodularis treatment is to stop the itch-scratch cycle and provide relief from the itching. Your doctor will first treat any underlying condition that is responsible for causing the itching and scratching.

The standard treatment for Prurigo nodularis includes using topical creams and systemic drugs in combination to give relief from the itching and scratching. Since the itching in Prurigo nodularis is so severe and every patient is different, you might have to undergo a trial-and-error process and try out several treatments to find out which combination works best for you.⁽¹²⁾

Being a rare disease, prurigo nodularis is still an understudied disease and not much is known about the condition. In some patients, no identifiable cause can be discovered for the itching. For such patients, there is no one effective treatment to get relief from the itching and nodules.

At present, there is only one approved therapy for the treatment of prurigo nodularis by the US Food and Drug Administration (FDA), and this too was only as recently as September 2022. The FDA approved Dupixent (dupilumab) injection for the treatment of Prurigo nodularis in adults.⁽¹³⁾ Apart from this, there are also several drugs that are used off-label for treating the condition. However, before using medications off-label, you should ensure that you discuss all the potential side effects with your doctor.

Before Dupixent, here are some of the other medications that were prescribed by doctors for treating prurigo nodularis.

1. Topical Drugs

   Your doctor is likely to begin the treatment with some over-the-counter (OTC) or prescription topical treatments to provide relief from the itching and also to soothe the skin. Some of these include:

   • Topical steroid creams like calcineurin inhibitors or clobetasol.
   • Topical vitamin D-3 ointment
   • Topical coal tar
   • Menthol
   • Capsaicin cream

2. Systemic Medications

   Your doctor may recommend some OTC or prescription antihistamines that will help you sleep better at night. They may also prescribe certain antidepressants to help stop the scratching. For example, medications like amitriptyline and paroxetine have been shown to successfully help the Prurigo nodularis nodules get better.

3. Injections

   Your doctor may recommend corticosteroid injections (Kenalog) for relieving some nodules.⁽¹⁴⁾

4. Other Treatments

   There are some other treatment options also available that may help relieve the itching and also shrink the nodule. These include:

   • Cryotherapy: This form of treatment makes use of extremely cold temperatures on the nodules.
   • Phototherapy: This therapy form uses ultraviolet light on the nodules and skin.
   • Pulsed dye laser: Pulsed dye laser is a method of treatment used to kill damaged or diseased skin cells.

Since the exact cause of the condition is not yet known, it is challenging to prevent the illness. The only way that seems possible is to not scratch your skin, especially if you have a family history of Prurigo nodularis or an underlying disease that increases the risk of getting Prurigo nodularis. If you have any long-lasting itching anywhere in the body, you should consult your doctor at the earliest to get it treated before the itch-scratch cycle begins.

Prurigo nodularis is a rare disease that causes extremely itchy skin with nodules or lesions. The condition causes such severe itching that it can be debilitating. The exact underlying cause of the illness is not understood completely, though it is associated with many other medical conditions. There are many treatments available, with the FDA recently approving an injection for treating Prurigo nodularis specifically. However, it may take some time to bring your Prurigo nodularis under control and in a manageable condition.

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