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.

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 very hard to treat, but current 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. Horiuchi et al in 2006 reported significant improvement in PN 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 by the US FDA in September 2022 to treat prurigo nodularis, the first such medication.

Prurigo nodularis was first described by Hyde and Montgomery in 1909.