Derm Dx: An elderly man with multiple intensely itchy dark red bumps

Prurigo nodularis is a skin condition of unknown etiology that generally arises secondary to itching or rubbing. Several conditions are common in patients with prurigo nodularis and are believed to play a role in inducing nodule formation, although it is...

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Prurigo nodularis is a skin condition of unknown etiology that generally arises secondary to itching or rubbing.

Several conditions are common in patients with prurigo nodularis and are believed to play a role in inducing nodule formation, although it is not completely understood how. These include: hepatitis, renal failure, psychiatric conditions, internal malignancy, HIV and other immune deficiencies.

As many as 80% of patients have personal or family history of atomic dermatitis, asthma or hay fever compared with about 25% of the general population. It is also possible that patients have no significant medical history.

Repetitive rubbing or scratching causes dark-colored nodules the can progress to plaques, nodular lichenification and hyperkeratosis. Patients often report intense pruritis of unknown cause at specific sites on the body and cannot control the urge to rub or scratch these sites.

Nodule pattern is often follicular, with lesions 3 to 20 mm in diameter that develop mostly on the arms and legs and sometimes the trunk. The nodules may be flat, umbilicated or crusted on top.

Although prurigo nodularis is benign and does not increase mortality, it can significantly affect a patient’s quality of life. Patient’s who experience the condition on large areas of the body may feel that it prevents them from performing functional activities.

Prurigo nodularis can occur at any age, but mostly affects middle aged and elderly patients.

Diagnosis

Histologic examination and cultures obtained from biopsied prurigo nodularis lesions may be necessary along with clinical presentation to rule out keratoacanthoma and fungal infections. Patch testing in patients with coexisting can be helpful in excluding contact sensitivity.

Physicians that suspect underlying hematologic malignancies, renal failure, and hepatic diseases should perform complete blood cell counts and liver function tests.

Treatment

Prurigo nodularis lesions are difficult to resolve and current treatments are mild-to-moderate at best. Combining several types of therapies may be necessary. These can include:

Typical pruritis meds such as menthol, phenol, pramoxine, casaicin cream, vitamin D-3 ointment and topical anesthetics

• Topical, oral and intralesional corticosteroids
• UV light treatment
• Antihistamines, anxiolytics, opiate receptor antogonists and thalidomine
• Habit reversal therapy to break the patient’s itch-scratch cycle
• Cryotherapy or pulse dye laser therapy, particularly for patients with diabetes or hypertension at risk for complications with other treatments
• Referral to an internist, family physician and/or psychiatrist for further investigation of underlying and coexisting conditions

Patients should be advised that complete lesion resolution is rare, and clinicians should strive to create a strong medical home as disease course is long and  symptoms may vary from mild to severe throughout.

References:

1.     Freedberg IM, Isin AZ, Wolff K, et al. Fitzpatrick’s Dermatology in General Medicine (5^th ed.). 1999. New York: McGraw-Hill.

2.     Hogan DJ. Prurigo nodularis. Medscape Reference. 2010.

3.     Elpern DJ. Int J Dermatol. 2009 Dec;48(12):1395-6.