Prurigo nodularis (PN), also known as nodular prurigo, is a

skin disease A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this sy ...

characterised by pruritic (

itch Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasant ...

y) 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 Lichen simplex chronicus (LSC) is thick leathery skin with exaggerated skin markings caused by sudden itching and excessive rubbing and scratching. It generally results in small bumps, patches, scratch marks and scale. It typically affects the ...

is a distinct clinical entity.

Signs and symptoms

* Nodules are discrete, generally symmetric, hyperpigmented or

purpuric Purpura () is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin secondary to platelet disorders, vascular disorders, coagulation disorders, ...

, and firm. They are greater than 0.5 cm in both width and depth (as opposed to

papules A papule is a small, well-defined bump in the skin. It may have a rounded, pointed or flat top, and may have a dip. It can appear with a stalk, be thread-like or look warty. It can be soft or firm and its surface may be rough or smooth. Some h ...

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 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 (also known as "Becker's melanosis", "Becker's pigmentary hamartoma", "nevoid melanosis", and "pigmented hairy epidermal nevus") is a benign skin disorder predominantly affecting males. The nevus can be present at birth, but more oft ...

, linear IgA disease, an autoimmune condition, liver disease and T cells. Systemic

pruritus Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasant ...

has been linked to cholestasis, thyroid disease, polycythaemia rubra vera, uraemia, Hodgkins disease,

HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...

and other immunodeficiency diseases. Internal malignancies, liver failure,

kidney failure Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney failure is classified as eit ...

, 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.

Pathophysiology

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. 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. * develop liver or kidney dysfunctions. * develop secondary skin infections. * have a personal or family history of

atopic dermatitis Atopic dermatitis (AD), also known as atopic eczema, is a long-term type of inflammation of the skin (dermatitis). It results in puritis, itchy, red, swollen, and cracked skin. Clear fluid may come from the affected areas, which often thickens o ...

. * have other autoimmune disorders. * have low

vitamin D Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...

levels.

Diagnosis

Diagnosis is based on visual examination and the presence of itching. A skin biopsy is often performed to exclude other diseases. Lesion biopsies usually show light inflammation, sometimes with increased numbers of

eosinophils Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. A ...

. 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,

Dupixent Dupilumab, sold under the brand name Dupixent, is a monoclonal antibody blocking interleukin 4 and interleukin 13, used for allergic diseases such as eczema (atopic dermatitis), asthma and nasal polyps which result in chronic sinusitis. It is ...

, vitamins,

cryosurgery Cryosurgery is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation. The term comes from the Greek words cryo (κρύο) ("icy cold") and surgery (''cheirourgiki'' – χ� ...

thalidomide Thalidomide, sold under the brand names Contergan and Thalomid among others, is a medication used to treat a number of cancers (including multiple myeloma), graft-versus-host disease, and a number of skin conditions including complications of ...

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 Prednisone is a glucocorticoid medication mostly used to immunosuppressive drug, suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium ...

, 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 Azathioprine (AZA), sold under the brand name Imuran, among others, is an immunosuppressive medication. It is used in rheumatoid arthritis, granulomatosis with polyangiitis, Crohn's disease, ulcerative colitis, and systemic lupus erythematosus, ...

, 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. Dupixent was the first medication approved by the FDA in September 2022 to treat Prurigo Nodularis.

History

Prurigo nodularis was first described by Hyde and Montgomery in 1909.Hyde JN, Montgomery FH: A practical treatise on disease of the skin for the use of students and practitioners. 1909; 174–175.

Notes

External links

DermNet NZ: Prurigo nodularis
* {{DermAtlas, -2016053621 Pruritic skin conditions Ailments of unknown cause