Prurigo nodularis

Prurigo nodularis (PN), also known as nodular prurigo, is a skin disorder characterized by pruritic (itchy), nodular lesions, which commonly appear on the trunk, arms and legs. Patients often present with multiple excoriated nodules caused by chronic scratching. Although the exact cause of PN is unknown, PN is associated with other dermatologic conditions such as untreated or severe atopic dermatitis and systemic causes of pruritus including liver disease and end stage kidney disease. The goal of treatment in PN is to decrease itching. PN is also known as Hyde prurigo nodularis, or Picker's nodules.
The exact cause of prurigo nodularis is unknown; however, it is thought to be induced by other dermatologic conditions such as severe atopic dermatitis, Becker's nevus, and linear IgA disease. PN is also associated with systemic causes of pruritus such as liver disease, cholestasis, thyroid disease, polycythemia vera, uremia, Hodgkins lymphoma, HIV and kidney failure diseases. Psychiatric illnesses have been considered to induce PN, although later research refuted a psychiatric cause for PN. Patients report an ongoing battle to distinguish themselves from those with psychiatric disorders, such as delusions of parasitosis and other psychiatric conditions.
Chronic and repetitive scratching, picking, or rubbing of the nodules may result in permanent changes to the skin, including nodular lichenification, hyperkeratosis, hyperpigmentation, and skin thickening. Unhealed, excoriated lesions are often scaly, crusted or scabbed. Many patients report a lack of wound healing even when medications relieve the itching and consequent scratching.
Patients often:
Diagnosis is based on visual examination and the presence of itching for greater than 6 weeks duration.
A skin biopsy is often performed to exclude other diseases. Lesion biopsies usually show light inflammation, sometimes with increased numbers of eosinophils. A culture of at least one lesion will rule out staphylococcus infection, which has been significantly linked to atopic dermatitis.
Prurigo nodularis is hard to treat and therapies include steroids, dupilumab, vitamins, cryosurgery, thalidomide, and UVB light. In the event that staphylococcus or other infection is present, antibiotics have proven effective, but tend to cause more harm than good for this particular disease. A physician may administer a strong dose of prednisone, which will almost immediately stop the itch/scratch cycle. However, cessation of steroids allows relapse to occur, usually within a few weeks. A 2006 study reported improvement in prurigo nodularis with antibiotic therapy.
Azathioprine, an immunosuppressive drug used in organ transplantation and autoimmune diseases belonging to the chemical class of purine analogues, also known by the brand name Imuran, has been reported to be effective.
Dupilumab (Dupixent) was approved for medical use in the United States in September 2022. Dupilumab is the first medication approved for the treatment of prurigo nodularis by the US Food and Drug Administration.
Nemolizumab (Nemluvio) was approved for medical use in the United States in August 2024.
Prurigo nodularis was first described by Hyde and Montgomery in 1909.