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.
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