Prurigo Nodularis

What is Prurigo Nodularis?

Prurigo Nodularis abbreviated as PN, is also referred to as Hyde prurigo nodularis, lichen corneus obtusus, Picker’s nodules, or the atypical nodula form of neurodermatitis. PN is a type of skin disorder characterized by the presence of some itchy nodules which are found on the arms and the legs of an affected person. Some may manifest multiple excoriated lesions as a result of scratching the pruritic skin area.

PN is considered as a bothersome or debilitating skin problem which can be noted to be in multiple, abraded nodules with severe itching felt, which develops on external surfaces of the limbs as a secondary result of rubbing in the area with very itchy firm lumps. This has been known to appear as the most severe existing form of prurigo.

Causes of Prurigo Nodularis

The main causative factor of PN is unknown, although it is found through some studies that it can be triggered with other existing conditions such as an autoimmune condition, Becker’s nevus, liver disease, problems of T cells in the body, linear IgA disease, renal failure, internal malignancies and some psychiatric illness. There are some recent studies that do not support PN to be related with psychiatric problems of patients, though these affected individuals are trying to set themselves apart from those having delusions of parasitosis and other psychiatric disorders.

Signs and Symptoms

Prurigo Nodularis has the tendency to affect all age groups but mostly noted among those between the ages of 20 to 60 years of age, where both males and females have equal chances to have the problem.

The first individual prurigo lump measures about 3mm to 20mm in diameter, presenting with raised protuberant surfaces of the skin, with a follicular pattern. It may start as a small, red itchy bump which may develop into some crusting and scaling after scratching the itchy lesions.

The appearance of older lesions may be darker or pale as compared to the surrounding skin. There is noted dryness in between the lesions. Patients often complain of very intense itchiness which may last for a couple of hours, leading to continuous scratching on that affected area with the risk of having a secondary infection after the integrity of the skin is broken.

PN lesions appear to be usually in groups and in numerous number from 1-2 to 200 counts per group. They are distributed symmetrically starting from areas of the lower arms and legs, and somewhat worse on its outer aspects.  Other areas of the body which can be affected could be the face, the trunk, and even the palms of the hands. During physical examination, these nodules can sometimes be more clearly seen on the neck, the shoulders and upper arms of a person.

Diagnosis

The clinical diagnosis of PN is made through a thorough visual examination of a patient’s skin and identifying specific areas as pointed with the presence of severe itching.

A skin biopsy can be initiated to confirm the diagnosis of PN and to exclude other disease conditions. The results under a histology study will usually show an increased level of eosinophils among individuals with PN.

Histopathology in cases of PN emphasizes a pathological reaction pattern which is marked by the presence of an enormously thickened skin which is abnormal, and can even be similar with the appearance of squamous cells in skin cancer.

There is an increase in the size of the nerve endings and the nerve fibers, and the skin becomes inflamed.  The increasing numbers of neural mediators found in the skin are proven to cause some nerve growth and itching in the area.

Treatment

PN is very hard to treat even by specialists and there is no standard approach yet on how to eradicate the problem since it has developed resistance in the administration of a family of wide-spectrum antibiotics.

There are other helpful methods to relieve the symptoms of PN and these are as follows:

• Oral antihistamines usually taken at bedtime to minimize the itchiness and it allow the person to rest and sleep.
• Corticosteroid injections using triamcinolone acetonide 10 – 40 mg /ml as prescribed for the presence of thicker nodules and lesions.
• Coal tar ointment which is used as an alternative for steroid.
• Application of emollients on affected areas of the skin to give a cooling and soothing effect.
• Capsaicin cream applied 4-6 times daily on affected areas as it induces burning sensation with itching, until the itching will completely stop.
• Calcipotriol ointment which is a topical vitamin D3 as an alternative for topical steroids.
• Application of ultra-potent topical steroid creams to relieve the itchiness.
• Cryotherapy can be helpful to shrink the existing nodules and lessen the itchiness of the skin.
• Pulsed dye laser can also be utilized to minimize the vascularity of individual lesions, leading to less skin itching of the patient.

Pictures

References:

Prurigo Nodularis – Overview, Presentation, DDx, Workup, Treatment, Medication, Follow-up at http://emedicine.medscape.com/article/1088032-overview#showall

Investigations in nodular prurigo, Treatment of nodular prurigo at http://www.dermnetnz.org/dermatitis/prurigo-nodularis.html

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.

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.

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.