Nodular prurigo, also known as prurigo nodularis, is a chronic skin condition characterized by the presence of multiple firm and itchy nodules. These nodules appear mainly on areas that are easy to reach, such as the arms, legs, shoulders, and upper back. The lesions are often thickened, hyperkeratotic, and may show signs of scratching, crusting, or scarring. The disease results from a persistent itch-scratch cycle, where repeated scratching leads to new lesion formation and worsening of itch sensations.
Over time, patients can develop dozens or even hundreds of nodules, which cause intense discomfort and often interfere with sleep and daily life. Although nodular prurigo is not life-threatening, it is chronic, difficult to manage, and has a major impact on physical and emotional well-being.
Why Does Nodular Prurigo Occur?
The cause of nodular prurigo is complex and involves multiple biological systems. It is now understood as a neuro-immunological disease, in which nerve hypersensitivity and immune dysregulation interact to maintain chronic itching. In the early stages, an external or internal trigger causes persistent itching. Scratching damages the skin barrier, releasing inflammatory mediators that attract immune cells to the area. These cells, including mast cells, eosinophils, and T-lymphocytes, release cytokines such as interleukin-4, interleukin-13, and interleukin-31, which amplify inflammation and stimulate sensory nerves that transmit itch signals. Repeated scratching thickens the skin and increases the density of nerve fibers, making the skin more sensitive to even mild stimuli.
How is Nodular Prurigo Diagnosed?
Diagnosis is usually based on the appearance of the lesions and the patient’s history of chronic itching. Doctors look for multiple firm, dome-shaped nodules that are distributed symmetrically on accessible areas of the body. The surrounding skin may show excoriations, lichenification, or secondary pigmentation. Lesions typically spare the palms, soles, and mucous membranes.
A detailed medical history helps identify potential triggers, associated systemic diseases, or medications that might cause itching. If the diagnosis is uncertain, a skin biopsy may be performed. Under the microscope, nodular prurigo shows thickened epidermis, marked hyperkeratosis, fibrosis of the dermis, and inflammatory cell infiltration. Increased numbers of nerve fibers can often be seen within the lesions. These findings help distinguish it from other chronic itchy skin conditions such as lichen simplex chronicus or hypertrophic lichen planus.
Because nodular prurigo may be associated with systemic illnesses, physicians often perform laboratory tests, including kidney and liver function tests, thyroid evaluation, and blood glucose screening. Identifying and managing these underlying factors can significantly improve outcomes. Assessing the severity of itching, lesion number, and impact on sleep or mood is also important, as these guide treatment decisions.
Can a Dermatoscope Detect Nodular Prurigo?
Dermoscopy, also known as dermatoscopy, can assist in the evaluation of nodular prurigo, although it is not a definitive diagnostic tool. Under dermoscopic examination, nodular prurigo shows characteristic surface and vascular patterns that reflect its chronic inflammatory and fibrotic nature. The most commonly reported dermoscopic findings include a central crust or erosion surrounded by white or pale-yellow areas representing hyperkeratosis and fibrosis. Peripheral dotted or linear vessels may be visible, corresponding to dilated capillaries caused by repeated scratching and chronic inflammation. In some cases, a peripheral pigmented network or brown-gray dots may appear, particularly in darker skin types, reflecting post-inflammatory pigmentation.
These features differ from those of other pruritic nodular lesions such as hypertrophic lichen planus or keratoacanthoma, which display distinct vascular and pigment structures. In hypertrophic lichen planus, dermoscopy typically reveals Wickham striae—fine white reticular lines representing areas of focal hypergranulosis—along with bluish-gray dots and streaks due to dermal melanin incontinence. In contrast, keratoacanthoma demonstrates a central keratin plug surrounded by hairpin or glomerular vessels arranged symmetrically, often on a pinkish background. These vascular structures are more regular and sharply demarcated than those in nodular prurigo, which tend to be irregular, peripheral, and associated with signs of chronic excoriation.
How is Nodular Prurigo Treated?
Treating nodular prurigo is challenging because of its chronic and relapsing nature. The main objectives are to break the itch-scratch cycle, reduce inflammation, relieve itching, and prevent new nodules from forming.
In mild cases, topical therapy is usually the first choice. Potent topical corticosteroids are commonly used to reduce inflammation and itching. Other topical options may include calcineurin inhibitors, vitamin D analogs, or capsaicin formulations, which desensitize nerve endings. Regular application of emollients is also important to restore the skin barrier and reduce irritation.
For moderate to severe disease, phototherapy such as ultraviolet B light may be helpful. When topical treatment is not enough, oral or systemic therapies are considered. These can include immunosuppressive drugs such as cyclosporine, methotrexate, or thalidomide. However, these medications require close medical supervision because of potential side effects.
Drugs that act on nerve function, such as gabapentin, pregabalin, or certain antidepressants, are sometimes used to reduce the sensation of itch. Newer targeted therapies are emerging that focus on specific immune pathways involved in chronic itching. These include biologic agents that block interleukin-4, interleukin-13, or interleukin-31 signaling, and newer oral Janus kinase inhibitors that can interrupt inflammatory and neural pathways. For ongoing skin maintenance, mild and non-irritating topical treatments can help soothe the skin and support healing.