Objectives of the registry

• To give insight on the natural course of disease in PP, namely reveal the burden of disease including frequency and severity of flares
• To reveal the need and efficacy of therapeutic interventions
• To reveal further genetic causes of PP
• To describe transcriptional profiles, correlating with subtypes and severity of disease

Primary and secondary endpoints

• Objective disease activity:

• Number of flares in the last 2 years (baseline) / since the last visit
• PGA (depending on PP subtype, further specified as GPP PGA, PPP PGA)
• PP area and severity score, namely GPP ASI, PPP ASI

• Quality of Life Scores

• DLQI
• EQ-5D
• WPAI-GH
• PSS 

• Patient reported outcomes:

• Disease activity VAS
• Pain VAS

The variable of primary interest (corresponding to an endpoint in a clinical trial) is the PGA / IGA severity grade, and as it is an observational study, both the first as well as all other visits are relevant.