In 1909, Hyde and Montgomery first described prurigo nodularis (PN) as pruritic nodules on the extensor surfaces of the lower extremities in middle-aged women.
Prurigo nodularis can be a bothersome-to-debilitating disease, usually seen as multiple, intensely pruritic, excoriated nodules erupting on the extensor surfaces of the limbs secondary to itching or rubbing. Prurigo nodularis is still a condition of unknown etiology. Many conditions have been reported to induce PN, from internal malignancy to renal failure to psychiatric conditions.
Chronic mechanical trauma to the skin causes thickening of the skin proportionate to the trauma. Repetitive rubbing, scratching, and touching (induced by a foreign body or self-induced) results in plaque or nodular lichenification and hyperkeratosis. Pigmentary changes often result from such repetitive trauma to the skin.
With prurigo nodularis, a person feels intense pruritus at discrete points and cannot control the urge to rub or scratch these points on the body. Any abnormality or explanation for the pruritus is unknown; scratching by the individuals who are affected is obvious. The results are discrete, nodular, hyperpigmented/purpuric lesions with surfaces that are scaly, excoriated, and possibly crusted.
Synonyms are Hyde prurigo nodularis, Picker nodules, lichen simplex chronicus, prurigo nodularis type, atypical nodular form of neurodermatitis circumscripta, lichen corneus obtusus, PN.