Assessment of Programmed Cell Death Protein 1 (PD-1) and Programmed Cell Death Ligand 1 (PD-L1) Tissue Expression Levels in Lichen Planus Patients: A Case-Control Study

This prospective Case Control study will be conducted at Kasr Al-Aini Dermatology Outpatient Clinics and will include 30 LP patients and 30 normal healthy controls which will be recruited and assessed for eligibility for inclusion according to the above criteria.

All participants (patients & controls) will be subjected to the following:

• Written informed consent.
• Detailed history including onset, course, duration of the disease and history of drug intake within 1 month before the eruption.
• Clinical assessment of the Severity by using LP Severity Index (LPSI) (Kaur et al., 2020).
• Skin biopsy will be taken under local anesthesia :
• From each normal control; a 3 mm punch skin biopsy from a sun protected area will be taken and preserved in PBS and kept frozen at -80 degrees Celsius for ELISA study.
• From each LP patient; two punch skin biopsies will be taken and preserved in PBS and kept frozen at -80 degrees Celsius for ELISA study:

i. The first biopsy will be a 3 mm punch biopsy from the center of LP lesional skin of sun protected area ii. The second biopsy will be a 3 mm punch biopsy from non lesional skin at least 15 cm away from the edge of any existing LP lesion of sun protected area

• The level of PD1 and PD-L1 will be detected using ELISA technique.
• The lesional biopsy will be assessed by routine hematoxylin and eosin (H&E) to confirm the diagnosis of LP
• Patients' serial numbers only will be used on data collection sheets and ELISA specimens' labels. Data will be entered on a computer with access limited to the researchers in order to ensure confidentiality of patients' information and lab results.