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Prurigo nodularis
 
 
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Prurigo nodularis (PN) is a skin disease characterised by pruritic (itch
Itch

Itch is an unpleasant sensation that evokes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience....
y) nodules which usually appear on the arms or legs. Patients often present with multiple excoriated
Excoriation

An excoriation is a punctate or linear abrasion produced by mechanical means, usually involving only the epidermis but not uncommonly reaching the papillary dermis....
 lesions caused by scratching. PN is also known as Hyde prurigo nodularis, Picker nodules, lichen simplex chronicus, atypical nodular form of neurodermatitis circumscripta, lichen corneus obtusus.


cause of prurigo nodularis is unknown, although other conditions may induce PN.






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Encyclopedia


Prurigo nodularis (PN) is a skin disease characterised by pruritic (itch
Itch

Itch is an unpleasant sensation that evokes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience....
y) nodules which usually appear on the arms or legs. Patients often present with multiple excoriated
Excoriation

An excoriation is a punctate or linear abrasion produced by mechanical means, usually involving only the epidermis but not uncommonly reaching the papillary dermis....
 lesions caused by scratching. PN is also known as Hyde prurigo nodularis, Picker nodules, lichen simplex chronicus, atypical nodular form of neurodermatitis circumscripta, lichen corneus obtusus.

Signs and symptoms

  • Nodules are discrete, generally symmetric, hyperpigmented or purpuric, and firm. They are greater than 0.5cm in both width and depth (as opposed to papules which are less than 0.5cm). 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.


Causes

The cause of prurigo nodularis is unknown, although other conditions may induce PN. PN has been linked to Becker's nevus
Becker's nevus

Becker's nevus is a skin disorder predominantly affecting males. The nevus generally first appears as an irregular pigmentation on the torso or upper arm , and gradually enlarges irregularly, becoming thickened and often hairy ....
, linear IgA disease, an autoimmune condition, and T cells. Systemic pruritus has been linked to cholestasis, thyroid disease, polycythaemia rubra vera, uraemia, Hodgkins disease, HIV
HIV

Human immunodeficiency virus is a lentivirus that can lead to AIDS , a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections....
 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.

Pathophysiology

Chronic
Chronic

Chronic may refer to:* Chronic , a persistent and lasting disease or medical condition, or one that has developed slowly* Chronic toxicity,* The Chronic, a 1992 album by Dr....
 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.

Patients often:
  • 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
    Atopic dermatitis

    Atopic dermatitis is an inflammation, chronically relapsing, non-contagious and pruritis skin disease. It has been given names like "prurigo Besnier," "neurodermitis," "endogenous eczema," "flexural eczema," "infantile eczema," and "prurigo diathsique"....
    .
  • have other autoimmune disorders.


Diagnosis

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
Eosinophil granulocyte

Eosinophil granulocytes, usually called eosinophils , are white blood cells that are one of the immune system components responsible for combating infection and parasites in vertebrates....
 in PN. A culture of at least one lesion will rule out staphylococcus infection, which has been significantly linked to atopic dermatitis.

Treatment

Prurigo nodularis is very hard to treat, but current therapies include steroids, vitamins, cryosurgery
Cryosurgery

Cryosurgery is the application of extreme cold to destroy abnormal or diseased tissue. The term comes from the Greek words cryo and surgery meaning "hand work" or "handiwork"....
, thalidomide
Thalidomide

Thalidomide is a sedative-hypnotic, and multiple myeloma medication. The drug is a potent Teratology in rabbits and primates including humans: this means that severe birth defects may result if the drug is taken during pregnancy....
 and UVB light
Light therapy

Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, for a prescribed amount of time and, in some cases, at a specific time of day....
. In the event that staphylococcus or other infection is present, antibiotics have proven effective. In at least one case, the root cause of PN was MRSA which was treated with intravenous vancomycin, affecting a complete cure(paper in progress; treat as anecdotal). A physician may administer a strong dose of prednisone
Prednisone

Prednisone is a synthetic corticosteroid drug that is usually taken orally but can be delivered by intramuscular injection and can be used for a number of different conditions....
, 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.

History

Prurigo nodularis was first described by Hyde and Montgomery in 1909.

See also

  • Pruritus
  • Skin lesion
    Skin lesion

    Most dermatoses present with skin lesions of more or less distinct characteristics. Macroscopically, these original lesions are known as the "primary lesion", and identification of such lesions is "...the most important aspect of dermatologic examination." However, these lesions may continue to develop or be modified by regression or trauma...


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