CTSL and psoriasis: Cysteine cathepsins are lysosomal peptidases that comprise cathepsin B and cathepsin L, which have many physiologic roles in different organs and tissues including cancer progression, tumor proliferation triggers, invasion, and metastasis,(10,11) and it has been demonstrated that abnormal concentrations and activities may correlate with various physiologic processes and human diseases, such as neurodegenerative disorders,(12) regulation of apoptosis, immune responses, inflammatory diseases,(13) cancer,(11,14,15) psoriasis,(16) and cardiovascular(17,18) and kidney diseases(19).