01/13/2026
Derm Index: Understanding Prurigo Nodularis
Prurigo nodularis (PN) is a chronic skin disorder characterized by the formation of hard, crusty nodules that cause intense itching. The condition often presents with nodules that may range in size, typically around half an inch in diameter, and are most commonly found on easily accessible areas such as the arms, shoulders, and legs. The hallmark symptom of PN is severe itching, which can persist day and night, with exacerbation occurring upon light touch or even clothing brushing against the skin. Scratching, which provides temporary relief, can exacerbate the condition, leading to further skin damage and a cycle of persistent itching.
Pathophysiology
Prurigo nodularis is thought to be primarily a consequence of neurogenic inflammation, driven by an abnormal response of skin nerve fibers to chronic itching. Initially, the sensation of itching can be triggered by various external or internal factors, but over time, scratching becomes habitual and leads to the thickening of skin nerves. This thickening, known as neurogenic remodeling, results in an exaggerated itch response to even mild stimuli, leading to a vicious cycle of scratching and further nerve sensitization. This phenomenon is often compared to “exercise” for the nerves, where repeated scratching increases the intensity of the itch signals.
Additionally, skin lesions in PN are marked by a thickening of the epidermis and dermis, and an accumulation of inflammatory cells, such as T-lymphocytes and mast cells, at the site of the nodules. This response indicates a complex interplay between skin inflammation and neuroimmune activation, which contributes to the persistence of itching and skin changes.
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