Characterizing Disease Features and Other Medical Diagnoses in Patients With Pityriasis Rubra Pilaris

Pityriasis rubra pilaris (PRP) is a rare papulosquamous disorder that normally manifests with hyperkeratotic follicular-based papules, scaling erythematous plaques with areas of sparing, and palmoplantar keratoderma.¹ Considerable heterogeneity exists in the clinical features of PRP. Not all patients experience progression to erythroderma, and PRP is sometimes associated with a seronegative arthritis.^1,2 The prevalence of arthropathy in PRP or frequency of other known disease features such as alopecia or anhidrosis is unknown.^3,4 In addition, the prevalence of other medical diagnoses in patients with PRP is incompletely described.

We conducted an online anonymous English survey-based study distributed via the PRP Facebook group (estimated 1505 patients) and a separate email list (474 patients), collecting 625 responses between July 5 and December 3, 2018. Overall, 319 patients were included. The survey is included in the Supplement. Patients were included if they were currently older than 18 years, were not also diagnosed with a potential PRP mimic (atopic dermatitis, psoriasis, dermatomyositis), and reported a PRP diagnosis confirmed by a dermatologist. Patients provided demographic data, self-selected symptoms they associated with PRP from a list of checkboxes, and reported other specific medical diagnoses they had received. All analyses were performed using SAS statistical software (version 9.4.3; SAS Institute, Inc). An institutional review board exemption was in place for this project at University of California, Los Angeles (UCLA), during data collection and initial data analysis, and at the University of Southern California (USC) during data analysis, to retrospectively study cutaneous erruptions including PRP. Institutional review board exemption numbers were (HS-18- 00640 for USC) and (17-000349 for UCLA).

From 625 survey responses, 319 (147 women [54.5%] and 296 White [95.5%]) patients met inclusion criteria (Table 1). Most reported a biopsy consistent with PRP (296 [92.8%]). Overall, 144 patients (45.1%) reported that a dermatologist specifically told them they had erythroderma, and 116 patients (36.4%) reported ectropion (Table 2). Arthralgia attributed to PRP by a dermatologist or rheumatologist was reported by 61 patients (19.1%). Other disease features frequently reported included nail changes (262 [82.1%]), inability to sweat (254 [79.6%]), and hair loss (200 [62.7%]).

Of the 17 medical conditions surveyed, the most frequent were allergic rhinitis (57 [17.9%]), depression (54 [16.9%]), cardiovascular disease (44 [13.8%]), nonmelanoma skin cancer (31 [9.7%]), type 2 diabetes mellitus (28 [8.8%]), other malignant abnormality (27 [8.5%]), hypothyroidism (26 [8.2%]), irritable bowel syndrome (23 [7.2%]), pulmonary disease (7 [2.2%]), and type 1 diabetes mellitus (6 [1.9%]). Fewer than 5 patients each reported diagnoses of vitiligo, celiac disease, inflammatory bowel disease, or myasthenia gravis.

With 319 patients, this study provides insights into disease features and medical diagnoses in a large sample of PRP patients. Reported prevalence of erythroderma has varied in the literature, but in this cohort, erythroderma occurred in 144 patients (45.1%), and ectropion in 116 patients (36.4%).¹ Anhidrosis is also a known feature of PRP and was reported by most patients in this study, but is infrequently discussed in recent medical literature.³ An appreciable proportion of patients (61 [19.1%]) reported arthralgia specifically attributed to PRP by their dermatologist or rheumatologist, suggesting further study of this disease feature is warranted, and that it may be more common than previously recognized.^2,5

Notably, 54 patients (16.9%) reported a depression diagnosis. The known negative effect of PRP on quality of life contextualizes this finding, and screening for depression with validated tools may thus be a helpful intervention.⁶ In addition, given literature suggesting associated underlying malignant or autoimmune diseases in some cases of PRP, these were important diagnoses to consider, but data were not sufficiently granular to assess the timing or relatedness of these diagnoses to PRP in each case.

Limitations to our study include the format of a support group-based survey study, which may represent patients with more severe disease. Data were self-reported, recall bias is likely, and this cohort was primarily White with minimal pediatric cases, limiting generalizability. Further research, both from a clinical and basic science perspective, will undoubtedly be needed to further understand PRP.

Accepted for Publication: July 10, 2020.

Corresponding Author: Katherine Halper, BA, Division of Dermatology at USC KSOM, 1450 San Pablo St, 2000, Los Angeles, CA 90033 (khalper@usc.edu).

Conflict of Interest Disclosures: None reported.

Published Online: September 23, 2020. doi:10.1001/jamadermatol.2020.3426

Author Contributions: Dr Maloney and Mr Lei had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Maloney, Kim, Ravi, Worswick, Lei.

Acquisition, analysis, or interpretation of data: Halper, Wright, Maloney, Worswick, Lei.

Drafting of the manuscript: Halper, Wright, Maloney, Kim, Lei.

Critical revision of the manuscript for important intellectual content: Halper, Wright, Maloney, Ravi, Worswick, Lei.

Statistical analysis: Maloney, Lei.

Administrative, technical, or material support: Maloney.

Supervision: Maloney, Worswick, Lei.

Additonal Contributions: We thank Michelle Hao, BA, for her contributions. We also thank Bill McCue, BA, and members of the PRP Facebook group for their great help in facilitating this study.