Nodularprurigo (NP) or prurigo nodularis is a chronic skin condition characterised by very itchy firm lumps. It can appear anywhere on the body but is most common on the arms, legs, back, and torso, in a symmetricaldistribution.
It is the most severe form of prurigo and thus can be difficult to treat.
Excoriated papules on the arms in nodular prurigo
Nodular prurigo on the arms
Excoriated prurigo lesions on the legs
Pigmentation of prurigo nodules in skin of colour (NP-patient3)
The exact cause of prurigo nodularis remains unknown. It is thought to relate to a dysregulation of the nerves as skin biopsies have shown a greater number of nerve cells in the dermis but a reduced amount in the epidermis. There is also an increased number of Merkel cells in the epidermis and the papillary layer of the dermis, as well as more neutrophils and mast cells, thus more cytokine release; which may explain the severe itchiness.
The itchiness may start as a result of an insect bite, stress, dermatitis, or another underlying skin or systemic condition. There is also an association with brachioradial pruritus, which results from traction of spinal nerves in the neck. Scratching will thicken and inflame skin, worsening the condition.
What are the clinical features of nodular prurigo?
Nodular prurigo can vary in severity, from a few to hundreds of lesions of varying size.
Initially, the rash:
Consists of small, red or pink bumps (usually 3–8 mm in diameter)
Is intensely itchy
Has a hyperpigmented border
Is located in easily accessible areas of the body – lateral aspects of the arms and legs, shoulders, chest, and buttocks
In some cases, presents as a papule before developing into a nodule or a plaque.
Scratching leads to:
Enlargement resulting in a nodular, raised, warty surface
Nodules tend to be firm and small but can measure up to 3 cm in diameter
Older nodules are normally darker and are surrounded by paler, dry skin
Nodules are grouped and follow a symmetrical distribution
How do clinical features vary in differing types of skin?
In darker skin, the lesions tend to be firmer, larger, and darker, similar to bumps on the skin that leave dark spots when healing, which can take longer to fade than in fairer skin types.
What are the complications of nodular prurigo?
Aside from its chronicity, the main complications are:
Automatic scratching behaviour that may develop in the absence of pruritus
Local infection.
How is nodular prurigo diagnosed?
Prurigo nodularis is most often diagnosed clinically, however, investigations are often useful particularly to ascertain the cause. These include:
Rarely, the blistering disease bullous pemphigoid can present as nodular prurigo (pemphigoid nodularis). Immunofluorescence reveals immunoglobulins in the BMZ below the epidermis. The prurigo nodules can be present for weeks or months before any blisters appear.
Patch testing — to determine any underlying allergen trigger
Blood tests — including FBC, liver, kidney, and thyroid function HIV tests to determine the presence of underlying systemic disease.
What is the differential diagnosis for nodular prurigo?
Unfortunately, there is no cure and treatment can be challenging. Therapy must be multimodal, also including treatment of any identified underlying condition.
In very severe, treatment-resistant lesions, immunosuppressive treatments such as short-course oral steroids, ciclosporin, methotrexate, or azathioprine can be prescribed to help reduce inflammation
Dupilumab (an anti-IL 4 and 13 inhibitormonoclonalantibody used to treat eczema, asthma and chronic rhinosinusitis) has shown efficacy in clearing treatment-resistant NP lesions.
The monoclonal antibody vixarelimab (targets the receptor for cytokines IL-31 and oncostatin M) and nemolizumab are currently being studied as a treatment for NP.
Promising results seen from an RCT for the treatment of NP with abrocitinib monotherapy.
General measures
It is crucial that anyone suffering from NP stops scratching the lesions, as this can make the condition worse. Strategies that can help include:
Keeping your mind busy
Covering the affected area with an occlusive dressing; hydrocolloids generally adhere well
Cooling the affected areas:
Laying a cool flannel on the skin may reduce inflammation and help ease the itching — some people keep flannels in the fridge for this purpose
Keep rooms to a cool temperature
Avoid sleeping with heavy or multiple bedclothes
Avoid wearing clothes made of synthetic fibres — cotton is preferable
Replace soaps or shower/bath gels that may irritate the skin with emollient
Prurigo nodularis can be difficult to treat, taking months or even years to clear and may not resolve completely, often rendering it a chronic condition. It is important that patients follow their dermatologist’s recommendations and report any issues with the treatment so that different approaches can be used.
Kowalski EH, Kneiber D, Valdebran M, Patel U, Amber KT. Treatment-resistant prurigo nodularis: challenges and solutions. Clin Cosmet Investig Dermatol. 2019;12:163–172. Published 2019 Feb 28. doi:10.2147/CCID.S188070 Journal
Müller S, Bieber T, Ständer S. Therapeutic potential of biologics in prurigo nodularis. Expert Opin Biol Ther. 2022;22(1):47–58. doi:10.1080/14712598.2021.1958777. Journal
Mullins TB, Sharma P, Riley CA, Sonthalia S. Prurigo Nodularis. In: StatPearls. Treasure Island (FL): StatPearls Publishing; September 14, 2021. PubMed
Wieser J, Mercurio M, Somers K. Resolution of treatment-refractory prurigo nodularis with dupilumab: a case series. Cureus. 2020 Jun;12(6):e8737. Journal
Williams KA, Huang AH, Belzberg M, Kwatra SG. Prurigo nodularis: Pathogenesis and management. J Am Acad Dermatol. 2020;83(6):1567–75. doi:10.1016/j.jaad.2020.04.182. Journal