Clinicopathological and management outcome in 70 patients with pityriasis rubra pilaris: A retrospective analysis.

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Background Pityriasis rubra pilaris (PRP) is a rare papulosquamous disease with a characteristic clinical appearance, including follicular salmon-coloured papules, which can sometimes progress into erythroderma. Both clinical and histopathological findings are important in diagnosing the disease and should be evaluated together. Objectives There are no guidelines for diagnosis and treatment of the disease. The aim of the present study was to contribute to the clinical diagnosis and treatment approach of this rare disease, which could serve as a clinical guide for dermatologists. Methods A total of 70 patients diagnosed with PRP in the last 20 years were included in this retrospective study. Clinical, demographic, and histopathologic profiles; and treatment strategies were analysed. Patients were divided into two groups with 'definite' or 'probable' diagnoses; those diagnosed to have PRP based on both clinical and histopathological findings were classified as having a 'definite' diagnosis; and those with histopathologically non-specific features but clinical findings compatible with PRP were classified as having a 'probable' diagnosis. Results Forty (57.1%) patients were females and 30 (42.9%) were males. Their age ranged from 8 to 79 years (mean age 39.57±18.80 years). The median duration of the disease (before patients received the diagnosis) was 7 months (IQR=24). According to biopsy reports, the most common epidermal changes were hyperkeratosis (78.6%) and focal parakeratosis (75.7%), while the 'checkerboard pattern,' which is considered specific for the disease, was detected in only 16 (22.9%) cases. Only 8 biopsy samples (11.4%) had an eosinophilic infiltrate. While 47 (67.1%) patients were classified under 'definite diagnosis and 23 (32.9%) were classified under 'probable diagnosis.' The disease duration was longer in patients with definite diagnosis than in patients with probable diagnosis (p=0.045). A total of 33 (47.14%) patients needed systemic therapy in addition to topical treatment. While 4 of these 33 patients were classified as Type 3, the remaining patients were classified as Type 1, classical adult type. Only three Type 1 (classical adult PRP) patients had erythroderma. Oral retinoids, especially acitretin, were the most preferred and effective treatment. Five patients showed improvement with methotrexate and two needed biological agents. Limitation The present study is retrospective and includes a relatively limited number of patients. Conclusion PRP is still a rare, difficult-to-manage disease. More studies are required to standardise and improve the diagnosis and treatment approaches for the disease.