Epidemiologic, Clinicopathologic, Diagnostic, and Management Challenges of Pityriasis Rubra Pilaris: A Case Series of 100 Patients

Importance Pityriasis rubra pilaris (PRP) is a rare papulosquamous disorder with limited epidemiologic and clinicopathologic data. Little information is available on long-term outcomes, comorbidities, and treatment efficacy. Objective To evaluate objective and subjective disease experience metrics from the perspectives of patients and clinicians. Design, Setting, and Participants One hundred patients with a putative diagnosis of PRP and who elected to participate completed a comprehensive survey, followed by acquisition of their medical records, including histopathology slides and reports. The data were analyzed separately from the health care clinician and the patient perspectives. Two academic dermatologists examined clinical notes, pathology reports, and photographs, confirming diagnoses via predetermined criteria. Patients were categorized into 4 levels of diagnostic certainty to allow stratification of the findings for subgroup analysis. Patients with a diagnosis of PRP were solicited through patient support organization websites. Main Outcomes and Measures Clinical outcomes, unexpected association of comorbidities, and efficacy (or lack of it) of various treatment modalities. Results Among the 100 patients, 50 were diagnosed as having classic, unquestionable PRP. The patients were a median of 61 years old (range, 5-87 years), and 46% were female. Fifty were categorized as level 1 diagnostic certainty, 15 as level 2, 30 as level 3, and 5 as level 4. Of the level 1 patients, 13 (26%) were correctly diagnosed at initial presentation; diagnosis was delayed, on average, by 29 months (range, 0.25-288 months; median, 2 months); and 27 (54%) having undergone 2 or more biopsies. At enrollment, PRP symptoms had persisted in 36 patients (72%) for an average of 58 months (range, 1-300 months; median, 30 months). Thirty-one patients (62%) had comorbidities, including hypothyroidism (20%). Nearly all patients (98%) received some form of therapy. Patients cited topical emollients, corticosteroids, and salicylic acid along with oral retinoids, methotrexate, and tumor necrosis factor inhibitors as most helpful. Conclusions and Relevance Pityriasis rubra pilaris remains a challenging diagnosis without established and specific treatment. Our data highlight new potential avenues for research with therapeutic perspective.