Definition:

Defects in lysosomal cysteine proteases (Cathepsins) are autosomal recessive lysosomal storage diseases. To date only following two human cathepsin deficiencies have been described, though there are eleven lysosomal cysteine proteases. Deficiency of cathepsin C leads to Papillon-Lefevre syndrome characterized by palmoplantar hyperkeratosis and severe early onset periodontitis. Deficiency of cathepsin K leads to pycnodysostosis characterized by osteosclerosis and short stature. Recent findings suggest a more expanded role for cathepsins in human biology.