Study Enhances Understanding of 'Tremendously Understudied' Prurigo Nodularis

Doug Brunk

April 19, 2021

Patients with prurigo nodularis tend to make a greater number of visits to health care specialists and are burdened by a greater number of medical comorbidities, compared with age-matched controls, as well those with atopic dermatitis and psoriasis.

Those are key findings from a retrospective analysis of claims data that was published online April 3, 2021, in the Journal of Investigative Dermatology.

"Prurigo nodularis is a tremendously understudied inflammatory skin disease," one of the study's cosenior authors, Shawn G. Kwatra, MD, of the department of dermatology, Johns Hopkins University, Baltimore, said in an interview. "Prurigo nodularis patients have uncontrolled itch, which leads to reduced quality of life, and the association with many disease comorbidities. We focused on better understanding in this work the unique comorbidities of prurigo nodularis, compared to other inflammatory skin diseases."

For the study, Kwatra, cosenior author Yevgeniy R. Semenov, MD, of the department of dermatology, Massachusetts General Hospital, Boston, and colleagues evaluated nationally representative, private insurance claims data from October 2015 to December 2019 to identify prurigo nodularis (PN) patients, who were defined as individuals with two or more medical claims for PN using ICD-10-CM codes. For comparison with patients with inflammatory skin diseases, they used the same claims data to identify patients with atopic dermatitis (AD) and psoriasis as well as to select controls who were age and gender matched to PN patients. Next, they quantified the overall comorbidity burden with the Charlson Comorbidity Index (CCI).

In 2016, the claims database included 2,658 patients with PN, 21,482 patients with AD, 21,073 patients with psoriasis, and 13,290 controls. The number of patients in each category rose each subsequent year, so that by the end of 2019 there were 9,426 patients with PN, 70,298 patients with AD, 59,509 patients with psoriasis, and 47,130 controls. Between 2016 and 2019 the mean age of PN patients increased from 57.5 to 59.8 years and the percent of male patients rose from 44.5% to 46.5%.

Between 2016 and 2019, the overall PN prevalence rates rose from 18 per 100,000 to 58 per 100,000, while the PN prevalence rates among adults increased from 22 per 100,000 to 70 per 100,000, and the rates among children rose grew from 2 per 100,000 to 7 per 100,000. "Our report shows an estimated disease prevalence of around 335,000 cases of PN in the United States," said Kwatra, who was among a group of researchers to recently report on systemic Th22-polarized inflammation in PN patients.

The researchers also found that patients with PN had the highest mean CCI in both 2016 and 2019. In 2016, their mean CCI was 1.53, compared with 0.98 among controls, 0.53 among those with AD, and 1.16 among those with psoriasis. In 2019, the mean CCI had increased in all groups of patients, to 2.32 among those with PN, 1.57 among controls, 0.75 among those with AD patients, and 1.71 among those with psoriasis.

The top five medical specialties who cared for PN patients, defined as the estimated number of visits per year per patient, were internal medicine (2.01 visits), dermatology (1.87 visits), family practice (1.60 visits), cardiology or cardiovascular disease (0.85 visits), and orthopedics or orthopedic surgery (0.49 visits).

"If you encounter a patient with prurigo nodularis, it's important to perform a screening for chronic kidney disease, diabetes, and liver disease," Kwatra said. "These comorbidities along with emerging studies on circulating blood biomarkers suggest prurigo nodularis is a systemic inflammatory disorder; thus systemic agents are needed for most patients as part of multimodal therapy in prurigo nodularis."

The researchers acknowledged certain limitations of the study, including its retrospective design and the identification of patients with PN with the ICD-10-CM code, which require further validation. "Furthermore, the increase in annual prevalence estimates for PN, AD, and psoriasis observed in the study could also be a result of increasing coding of these diagnoses in the claims data along with rising awareness by the medical profession," they wrote.

Kwatra disclosed that he is an advisory board member/consultant for AbbVie, Galderma, Incyte, Pfizer, Regeneron, and Kiniksa Pharmaceuticals, and has received grant funding from Galderma, Pfizer, and Kiniksa. He has also received a Dermatology Foundation Medical Dermatology Career Development Award, a research grant from the Skin of Color Society, and is supported by the National Institutes of Health. One coauthor has been funded by NIH grants.

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