 [ Symptoms ] my father has been diagnosed with brain tumor – requires surgery medication or other treatment [ Disease ] both pycnodysostosis and osteoporosis cause brittle bones however pycnodysostosis is a disease with abnormally dense bones whereas osteoporosis is exactly the opposite a disease with washed out porous bones there would seem to be no conceivable connection between pycnodysostosis and osteoporosis the new findings about cathepsin k and pycnodysostosis have made it clear that cathepsin k is a major protease in bone resorption given this function it may well have a role in osteoporosis cathepsin k may in fact provide a rational basis for a new approach to the treatment of osteoporosis this is an excellent illustration of how research on a rare disease may bring benefits to those affected by a common disease