Prurigo nodularis (PN), also known as nodular prurigo, 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.
|Pruritic papules and scattered nodules can be seen (a) on the legs, (b) on the arms and (c) on the trunk of this patient with prurigo nodularis.|
|Classification and external resources|
Lichen simplex chronicus is a distinct clinical entity.
Signs and symptomsEdit
- 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 have been considered to 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.
- have low vitamin D levels.
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.
Another drug a physician may administer is Apo-Azathioprine. Azathioprine, also known by its brand name Imuran, is an immunosuppressive drug used in organ transplantation and autoimmune diseases and belongs to the chemical class of purine analogues.
Prurigo nodularis was first described by Hyde and Montgomery in 1909.
- Lockshin BN, Brogan B, Billings S, Billings S (2006). "Eczematous dermatitis and prurigo nodularis confined to a Becker's nevus". Int. J. Dermatol. 45 (12): 1465–1466. doi:10.1111/j.1365-4632.2006.02971.x. PMID 17184268.
- 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.
- Hazin R, Abu-Rajab Tamimi TI, Abuzetun JY, Zein NN. Recognizing and treating cutaneous signs of liver disease. Cleve Clin J Med 76(10) pp. 599-606, 2009. PMID 19797460
- Sonkoly E, Muller A, Lauerma AI, et al. (2006). "IL-31: a new link between T cells and pruritus in atopic skin inflammation". J. Allergy Clin. Immunol. 117 (2): 411–7. doi:10.1016/j.jaci.2005.10.033. PMID 16461142.
- Hiramanek N (2004). "Itch: a symptom of occult disease". Australian family physician. 33 (7): 495–9. PMID 15301165.
- Berger TG, Hoffman C, Thieberg MD (1995). "Prurigo nodularis and photosensitivity in AIDS: treatment with thalidomide". J. Am. Acad. Dermatol. 33 (5 Pt 1): 837–8. doi:10.1016/0190-9622(95)91846-9. PMID 7593791.
- Kieć-Swierczyńska M, Dudek B, Krecisz B, et al. (2006). "[The role of psychological factors and psychiatric disorders in skin diseases]" [The role of psychological factors and psychiatric disorders in skin diseases]. Med Pr (in Polish). 57 (6): 551–5. PMID 17533993.
- Vargas Laguna E, Peña Payero ML, Vargas Márquez A (Dec 2006). "[Influence of anxiety in diverse cutaneous diseases]" [Influence of anxiety in diverse cutaneous diseases]. Actas Dermosifiliogr (in Spanish). 97 (10): 637–43. PMID 17173825.[permanent dead link]
- Johansson O, Liang Y, Marcusson JA, Reimert CM (2000). "Eosinophil cationic protein- and eosinophil-derived neurotoxin/eosinophil protein X-immunoreactive eosinophils in prurigo nodularis". Arch. Dermatol. Res. 292 (8): 371–8. doi:10.1007/s004030000142. PMID 10994770.
- 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.
- Lin YT, Wang CT, Chiang BL (Dec 2007). "Role of bacterial pathogens in atopic dermatitis". Clin Rev Allergy Immunol. 33 (3): 167–77. doi:10.1007/s12016-007-0044-5. PMID 18163223.
- 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.