Prurigo Nodularis - Causes and Treatment

Introduction:

Prurigo nodularis is a long-term disorder of the skin. It is commonly associated with other diseases, such as atopic dermatitis or any dermatoses associated with chronic pruritus (itchy skin often caused by dry skin). The therapeutic approach widely acts as a powerful antipruritic, immunomodulatory. Treatment is prolonged, and patient compliance with education and counseling is essential. The interprofessional team's role is to care for patients with this condition. The lesions are very pruritic, and this condition may occur in any age group since it is commonly associated with some other disorder of cutaneous hypersensitivities such as atopic dermatitis or chronic pruritus. Therefore, the diagnosis is mainly based on clinical examination. In addition, this condition is seen with significant physical and psychological morbidity and refractory treatments. Therefore, general measures, pharmacological approaches, and psychological therapies may be needed in patients with advanced prurigo nodularis.

What Is Nodular Prurigo Nodularis?

Nodular prurigo (NP) or prurigo nodularis is a long-term skin condition characterized by very itchy, firm lumps that can appear anywhere on the body. It is most commonly seen on the arms, legs, back, and torso in symmetrical distribution and is the most severe form of prurigo, which is challenging to treat.

Who Gets Nodular Prurigo?

• Nodular prurigo can affect both sexes and people of all age groups but is more common in older adults.

• There is also an association with atopy (predisposition to asthma, atopic dermatitis, and hay fever).

• Drugs that produce chronic itches, such as antimalarials, opioids, and targeted cancer treatments.

• Internal diseases such as:

• Cancer.

• Diabetes.

• Liver disease.

• Chronic kidney disease.

• HIV/AIDS - Human immunodeficiency virus / acquired immunodeficiency syndrome.

• Thyroid disorders.

What Causes Nodular Prurigo?

The exact cause of the disorder prurigo nodularis remains unknown. Thought relates to a dysregulation of the nerves as the skin biopsies showed a more significant number of nerve cells in the dermis. Still, there is a reduced amount in the epidermis. There is an increased number of Merkel cells in the epidermis and the papillary layer of the dermis, as well as more neutrophils and mast cells, which have more cytokine to release, which may explain the severe itchiness. The itchiness may start due to an insect bite, stress, dermatitis, or another underlying skin or systematic condition. There is also an association with brachioradialis pruritus (which causes itching and stinging or tingling sensations in the area of the outer forearm), which results from the traction of spinal nerves in the neck, where scratching will thicken and inflame the skin, worsening the condition.

What Are the Clinical Features Seen in Nodular Prurigo?

Clinical features of nodular prurigo severity vary from a few to hundreds of lesions. Initially, the rash is formed:

• Consisting of small, red, or pink bumps.

• It is intensely itchy.

• Have hyperpigmented borders.

• Located on the readily accessible areas of the body, lateral aspects of the arms, legs, shoulders, chest, and buttocks.

• Sometimes, it presents as a papule that develops into a nodule or a plaque.

Scratching leads to the following conditions:

• Where the enlargement results in a nodular, raised, warty surface.

• Where the nodules tend to be more firm and small but can also measure up to 3 cm in diameter

• Older nodules are usually significantly darker and surrounded by paler, dry skin.

• Where the nodules are grouped and follow a symmetrical distribution.

• In which some may ulcerate, increasing infection risk.

• The healed lesions can leave a scar or discoloration.

• In which affected skin may harden and thicken.

How Do Clinical Features Vary in Different Skin Types, and What Are the Complications of Prurigo nodularis?

In darker-skinned patients, the lesions tend to be firmer, more prominent, and darker, similar to bumps on the skin, which leave dark spots while healing. It takes longer to fade than in fairer skin types. Asides from their chronicity, the main complications seen are:

• Mechanical scratching behavior may develop in the absence of pruritus.

• Local infections.

How Is Nodular Prurigo Nodularis Diagnosed?

Prurigo nodularis is most often clinically diagnosed by investigations used particularly to a specific cause, including:

• Skin Biopsy - It is used to confirm the diagnosis.

• Nerve endings and fibers are markedly increased in size.

• An increased number of neural mediators are there to cause itching and nerve growth.

• Inflammation on the affected area.

• Direct Immunofluorescence- They are generally negative.

• Rarely blistering disease shows bullous pemphigoid that can present as nodular prurigo (pemphigoid nodularis). Immunofluorescence reveals immunoglobulins below the epidermis layer. The prurigo nodules may present for weeks or months before any blisters can appear.

• Patch testing to find any underlying allergen trigger.

• Blood tests, including liver, kidney, and thyroid function HIV tests, determine the underlying systemic disease.

What Is the Differential Diagnosis of Prurigo nodularis?

• Atopic Dermatitis- It is a condition causing dry, itchy, and inflamed skin and is expected in children at any age.

• Pemphigoid Nodularis - It is a rare form of bullous pemphigoid.

• Actinic Prurigo: It is an intensely itchy form of skin condition caused by an abnormal reaction to sunlight.

• Epidermolysis Bullosa Pruriginosa- It is a rare skin disorder in which the skin becomes fragile.

• Lichen Simplex- It is a chronic disorder caused by repeated scratching and itching.

• Lichen Planus - It is a condition that causes swelling and irritation in the skin, hair, nails, and mucous membranes.

• Dermatillomania - It is a mental illness causing repeated skin picking that results in tissue damage.

What Is the Treatment of Prurigo nodularis?

Prurigo nodularis is not cured completely, and treatment may be challenging. Therefore, treatment therapy must be multimodal, including treatment of any identified underlying condition.

• Specific Measures: Standard treatment options include the following:

• Topical emollients.

• Topical steroid cream or ointment, usually ultra-powerful steroids, are applied under hydrocolloid dressing or paste bandage occlusion or with steroid-impregnated tape.

• Topical capsaicin and Tacrolimus 0.1 % ointment for itching.

• Calcipotriol or Betamethasone ointment is used.

• Sedating type of oral histamines.

• Phototherapy with either UVB or photochemotherapy (PUVA).

• Systemic treatment with Gabapentin, Pregabalin, and Naltrexone.

• Occasionally, antibiotics are used to treat locally infected skin (cellulitis).

Other treatment options include the following:

• Cryosurgery or excimer lasers are used to treat nodular lesions.

• For patients with severe treatment-resistant lesions, immunosuppressive treatment, such as short-course oral steroids, Cyclosporine, and Methotrexate, is prescribed to help reduce inflammation.

• Thalidomide used in recalcitrant cases.

• Dupilumab has shown efficiency in clearing treatment-resistant prurigo nodularis lesions.

• General Measures: Anyone suffering from prurigo nodularis must stop scratching the lesions, which can worsen the condition. Strategies that can help include the following:

• Keeping the mind busy.

• Cooling the affected areas by laying a cool flannel on the skin may reduce the inflammation and help ease the itching - some people keep the flannels inside the fridge for this purpose.

• To keep the room temperature cool.

• Avoid wearing clothes made of synthetic fibers - where cotton is preferred most.

• Replace the soaps, shower, or bath gels that may irritate the skin with emollients.

• Apply emollients at least twice daily, especially if the person has dry skin.

Conclusion:

Prurigo nodularis is challenging to treat; it may take months or even years to clear and not resolve entirely since it is a chronic condition. Therefore, the patients need to follow their dermatologists to report any issues in the treatment so that different approaches can be used to treat them.