Paraneoplastic pityriasis rubra pilaris: a systematic review.

[BACKGROUND] Paraneoplastic pityriasis rubra pilaris (PRP) is a rare and poorly defined chronic inflammatory skin condition. Recognition of its potential association with cancer is crucial to facilitate timely diagnosis and treatment.

[OBJECTIVES] To summarize published literature on paraneoplastic PRP, with a focus on associated cancer types, latency periods, treatment outcomes and resolution following oncological management.

[METHODS] A literature review was conducted following PRISMA guidelines using the MEDLINE, Embase, Cochrane Library and Web of Science databases. Search terms used were 'pityriasis rubra pilaris', 'malignancy', 'cancer' and 'paraneoplastic', and inclusion criteria were adults diagnosed with both cancer and probable paraneoplastic PRP. Two authors independently reviewed the titles and abstracts of all identified papers before the full text of potentially relevant studies was retrieved for further analysis.

[RESULTS] From 978 articles screened, 22 studies describing 23 adult patients were included. Solid tumours were implicated in 83% of cases (n = 19/23), with lung cancer the most common of these (n = 7/19, 37%). The median latency from PRP onset to cancer diagnosis was 9 weeks [interquartile range (IQR): 0.4-25.0]. Among 17 patients experiencing complete or partial resolution of PRP following treatment for their cancer, complete resolution occurred in 65% (n = 11/17), typically within a median of 11 weeks (IQR: 6.8-22.8). The overall mortality rate in evaluable cases was 16% (n = 3/19).

[CONCLUSIONS] In this systematic review, paraneoplastic PRP was associated with multiple types of cancer, both solid and haematological. Cancer screening should be considered in cases of atypical or treatment-refractory PRP. Further prospective studies are required to define predictive features and optimize diagnostic approaches.