What is tendinitis? Tendinitis is swelling and pain in a tendon, which is tissue that connects muscles to bones. It is a common condition, usually caused by repeated injuries to a tendon.
What is pachyonychia congenita? Pachyonychia congenita (PC) is a very rare genetic disorder that affects the skin and nails. Most people have thickened nails and calluses on the bottom of the feet. Painful calluses on the soles can make walking difficult. Because of the pain, some people rely on a cane, crutches, or a wheelchair to help with walking.