'Actinic Prurigo': A Phrase Describing Four Different Diseases in Four Different Continents: Systematic Review and Analysis.

Background: There are no internationally agreed diagnostic criteria for actinic prurigo.

Objective: To analyze the clinical features of all patients ever reported in the medical literature with a diagnosis of 'actinic prurigo'.

Methods: A systematic literature review of all case reports, case series and retrospective studies published since 1946 about patients given a diagnosis of actinic prurigo. We tested our hypothesis that the patients divide into four clinically distinctive presentations: 'eczematous patch' (EP), 'papular' (P), 'labial' (L) or 'nodular' (N). We divided the papers analysed into these four categories by initial qualitative assessment and then tested our hypothesis of four clinically distinct subtypes by detailed quantitative analysis.

Results: Quantitative analysis confirmed the hypothesis that there are four clinically distinct subtypes of actinic prurigo: 'eczematous patch' (EP), 'papular' (P), 'labial' (L) and 'nodular' (N). They differ significantly in clinical features, geographical location, ethnicity of patients and HLA typing. All the subtypes are photosensitive inflammatory dermatoses, with the greatest overlap is between the 'EP' and 'P' subtypes.

Conclusion: We propose a new nomenclature for actinic prurigo to include these four subtypes. This improved diagnostic definition should make it easier to define the natural history of this disease and identify effective treatments.

Prospero: CRD42018085694.