|Classification and external resources|
Prurigo nodularis (PN) is a skin disease characterised by pruritic (itchy) nodules which usually appear on the arms or legs. Patients often present with multiple excoriated lesions caused by scratching. PN is also known as Hyde prurigo nodularis, Picker's nodules, atypical nodular form of neurodermatitis circumscripta, lichen corneus obtusus.
Lichen simplex chronicus is a distinct clinical entity.
Signs and symptoms
- Nodules are discrete, generally symmetric, hyperpigmented or purpuric, and firm. They are greater than 0.5 cm in both width and depth (as opposed to papules which are less than 0.5 cm). They can appear on any part of the body, but generally begin on the arms and legs.
- Excoriated lesions are often flat, umbilicated, or have a crusted top.
- Nodules may appear to begin in the hair follicles.
- Nodule pattern may be follicular.
- In true prurigo nodularis, a nodule forms before any itching begins. Typically, these nodules are extremely pruritic and are alleviated only by steroids.
The cause of prurigo nodularis is unknown, although other conditions may induce PN. PN has been linked to Becker's nevus, linear IgA disease, an autoimmune condition, liver disease  and T cells. Systemic pruritus has been linked to cholestasis, thyroid disease, polycythaemia rubra vera, uraemia, Hodgkins disease, HIV and other immunodeficiency diseases. Internal malignancies, liver failure, renal failure, and psychiatric illnesses may induce PN, although more recent research has 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 subsequent scratching.
- seek treatment during middle-age, although PN can occur at any age.
- have a history of chronic severe pruritus.
- have a significant medical history for unrelated conditions.
- suffer from liver or kidney dysfunctions.
- suffer secondary skin infections.
- have a personal or family history of atopic dermatitis.
- have other autoimmune disorders.
Diagnosis is based on visual examination and the presence of itching. A skin biopsy is often performed to exclude other diseases. Lesion biopsies will typically show a high level of eosinophils in PN. 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, 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. recently reported significant improvement in PN with antibiotic therapy.
Prurigo nodularis was first described by Hyde and Montgomery in 1909.
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- Torchia D, Caproni M, Del Bianco E, Cozzani E, Ketabchi S, Fabbri P (2006). "Linear IgA disease presenting as prurigo nodularis". Br. J. Dermatol. 155 (2): 479–80. doi:10.1111/j.1365-2133.2006.07315.x. PMID 16882196.
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- Gong JQ, Lin L, Lin T et al. (Oct 2006). "Skin colonization by Staphylococcus aureus in patients with eczema and atopic dermatitis and relevant combined topical therapy: a double-blind multicentre randomized controlled trial". Br J Dermatol. 155 (4): 680–7. doi:10.1111/j.1365-2133.2006.07410.x. PMID 16965415.
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- Guzik TJ, Bzowska M, Kasprowicz A et al. (Apr 2005). "Persistent skin colonization with Staphylococcus aureus in atopic dermatitis: relationship to clinical and immunological parameters". Clin Exp Allergy 35 (4): 448–55. doi:10.1111/j.1365-2222.2005.02210.x. PMID 15836752.
- Horiuchi Y, Bae S, Katayama I (2006). "Uncontrollable prurigo nodularis effectively treated by roxithromycin and tranilast". Journal of drugs in dermatology : JDD 5 (4): 363–5. PMID 16673805.
- Hyde JN, Montgomery FH: A practical treatise on disease of the skin for the use of students and practitioners. 1909; 174–175.
- Cure Prurigo Nodularis - Informative & Support Site
- DermNet NZ: Prurigo nodularis
- DermAtlas -2016053621
- Nodular Prurigo UK: Support Website