Nodular prurigo (NP), also known as prurigo nodularis, is a chronic dermatological disorder characterized by intensely pruritic, firm nodules. Although it can form anywhere on the body, a symmetrical distribution of arms, legs, back, and torso is where it most frequently appears.
It is still unclear what specifically causes NP. Based on skin biopsies, it is believed to be related to a dysregulation of the nerves, with more nerve cells seen in the dermis and fewer in the epidermis.
There is also an association with atopy, certain drugs, and systemic conditions such as chronic kidney disease, liver disease, diabetes, and malignancy.
The severity of NP can range from a few to hundreds of lesions of different sizes.
At first, the rash:
– Include tiny, red, or pink bumps typically 3–8 mm in diameter.
– Has a hyperpigmented border
– Very itchy
– Is distributed in readily accessible body regions, including the lateral aspects of the arms and legs, shoulders, chest, and buttocks.
Sometimes, it begins as a papule and progresses to a nodule or plaque.
Scratching results in:
-Enlargement producing a raised, warty, nodular surface. The nodules have a symmetrical distribution and are usually hard and small, but they can reach up to 3 cm in diameter.
-Ulceration of the skin that can lead to an increased risk of infection.
-Healed lesions may leave a scar or discoloration.
The diagnosis of NP is clinical, based upon the clinical presentation of distinctive excoriated, nodular lesions frequently distributed symmetrically and a patient’s history of persistent, intense pruritus. A skin biopsy is not routinely performed to confirm the diagnosis.
It is essential to evaluate systemic causes of persistent pruritus in individuals with NP who do not have a history of atopic dermatitis or other pruritic skin disorders. These causes may include chronic kidney disease, liver disease, thyroid disease, HIV infection, parasite infestation, or malignancy. The initial laboratory and imaging evaluation may consist of:
- Complete blood cell count
- Liver function tests
- Blood urea nitrogen and creatinine
- Thyroid-stimulating hormone
- HIV test
- Stool examination for ova and parasites
- Chest radiograph
A complex and multi-modal strategy is necessary for the treatment of NP which includes:
- Instructing patients on various ways to reduce skin itching and scratching
- Treating pruritus symptoms
- Topical or systemic therapies that target the itch-scratch cycle and minimize skin lesions
Common treatment options include:
- Topical emollients
- Topical steroid cream or ointment — usually ultrapotent steroid and applied under hydrocolloid dressing or paste bandage occlusion, or steroid impregnated tape
- Topical capsaicin and tacrolimus 0.1% ointment for itch
- Local corticosteroid injection into the nodules to reduce inflammation
- Sedating oral antihistamines
- Phototherapy with either UVB or photochemotherapy (PUVA)
- Systemic treatment with gabapentin, pregabalin, and naltrexone
- Occasionally, antibiotics may be used to treat locally infected skin (cellulitis).
Mashael Alanazi, Medical student.
Maee Barakeh, Medical student.