NEW YORK – Once it reaches the plaque stage, prurigo nodularis becomes extremely difficult to control with currently available topical and systemic therapies, according to a comprehensive summary presented at the American Academy of Dermatology summer meeting.
When treatment begins at an advanced stage, “it takes years until we see a complete relief,” reported Dr. Sonja Stander of the Center for Chronic Pruritus, University Hospital Muenster (Germany). Conveying this information to the patient is “very essential” to develop realistic expectations and to enlist cooperation in the frequent treatment modifications needed to achieve maximum relief.
Dr. Sonja Stander
Prurigo nodularis is characterized by a symmetrical distribution of very itchy, hyperkeratotic, erosive nodules and papules. Scratching contributes to the “chronification” and the progression that typically takes patients from papules to nodules to plaques, according to Dr. Stander, an expert who has joined with others to create the Prurigo Nodularis League (PNL) to raise awareness about the condition.
Information on more than 600 prurigo nodularis patients has been collected in a database created by the PNL, which is designed to consolidate information on the epidemiology, pathology, and treatments for a condition that Dr. Stander said many patients describe as “agonizing” or “horrendous.” The condition has been linked to a variety of systemic and neurologic diseases, but the underlying mechanism of this condition remains poorly understood.
Until recently, commonly used first-line treatment strategies, which include PUVA, topical steroids, and the immunomodulatory agent pimecrolimus, were employed primarily on the basis of case series and expert opinion. She reported that only three randomized, controlled trials have been published relating to these approaches. All involved topical treatments.
“Do you think this is enough for treating the prurigo patient? Topical treatment? No way, but we do not have data from trials with systemic therapies,” reported Dr. Stander, who provided an algorithm that begins with topical therapies but quickly moves to second- and third-line systemic agents. Dr. Stander noted, however, that independent phase 2 trials were recently initiated with the NK1 receptor antagonists aprepitant and serlopitant, providing hope that there are “some new drugs on the horizon.”
According to Dr. Stander, European guidelines for prurigo nodularis recommend topical capsaicin and naltrexone for initial therapy. Both are used off label, but she believes both produce benefit. Other therapies supported by case studies include the neuromodulator gabapentin, the immunomodulator methotrexate, and selective serotonin receptor inhibitors. The side effects of most of these therapies, particularly drugs such as methotrexate, typically precede the benefits, according to Dr. Stander, who reiterated that patients must be warned about the slow pace of improvement.
It is hoped that the PNL database will provide enough patients to permit patterns in disease etiology to be discerned. One of the questions is where atopy, which Dr. Stander said is a prominent feature in about 50% of prurigo nodularis patients, plays a role. She explored the theory that this prurigo nodularis represents a neuropathy of the skin, citing evidence of differences in nerve fiber density in the dermal and epidermal layers of these patients when compared with individuals without this condition.
The differential diagnosis includes autoimmune diseases, such as bullous pemphigoid. In fact, Dr. Stander reported that she screens for bullous pemphigoid in every patient suspected of prurigo nodularis.
One of the peculiar features of prurigo nodularis is that there appears to be no correlation between the duration of this condition and its intensity. Rather, most patients “start with a very severe pruritus” with skin lesions exacerbated by scratching, according to Dr. Stander. She said that although it was once thought that a plaque presentation might represent a different subtype, it is now believed that this is simply an advanced stage.
Encouraging physicians who encounter prurigo nodularis to contribute cases to the database, Dr. Stander reported that “we want to raise awareness for this severe entity” through the PNL. She said the PNL website is a repository for information and invites comments to allow information to be exchanged.
Dr. Stander reported no financial relationships to disclose.