Prurigo nodularis is a debilitating chronic skin disorder characterized by severely itchy, crunchy, firm papules and nodules that often appear on the arms and legs, but may appear diffuse on the body. The pathogenesis of prurigo nodularis is poorly understood because this condition is associated with a wide range of primary skin and underlying medical conditions affecting the liver, kidneys and blood.
Regardless of the cause of these lesions, the impact on quality of life for these patients can be enormous, because the itching associated with the lesions can both worsen and cause stress, causing the itchy scratch cycle to continue and further lesion formation induced. Many of the treatment options, including topical agents, phototherapy and systemic immunomodulators, show limited promise due to side effects and low efficacy.
A team from George Washington University (GW) has conducted a systematic review of clinical trials investigating treatment with prurigo nodularis, published between 1990 and the present, with at least five subjects.
"Currently there is a lack of targeted pharmacological therapy for prurigo nodularis and all used treatment methods show varying degrees of success," said Adam Friedman, MD, professor of dermatology at the GW School of Medicine and Health Sciences and senior author of the study. "We wanted to provide a summary of evidence-based treatments to highlight the promising directions and also underline areas that need improvement."
Friedman and his team looked at 35 studies with differences in factors such as the number of subjects and the delivery of the treatment. They gave a score for each study, in which the efficacy and consistency were compared to prurigo nodularis.
In the review, the team found the most promising in new treatments, such as neurokinin-1 receptor antagonists, part of a class of medicines used to treat nausea and vomiting associated with chemotherapy. The receptor is a target of substance P, a mediator of itching and a likely pathogenic agent of prurigo nodularis.
"By determining which current and future therapies are effective for prurigo nodularis, we can gain a better understanding of the biological underpinning of this disease and patients will ultimately benefit from better treatment options," Friedman said. "Our summary provides not only guidelines for practitioners regarding the wide range of off-label therapies in our armaments, but also for researchers in identifying gaps in the development of treatments."
The team suggests that more powerful studies and additional randomized controlled trials are needed to better assess treatment options for prurigo nodularis.