What is juvenile idiopathic arthritis (JIA)? Juvenile idiopathic arthritis (JIA) is the most common type of chronic, or long-lasting, arthritis that affects children. It happens when the immune system attacks healthy joint tissues. JIA broadly refers to several different chronic (long-lasting) disorders involving inflammation of joints (arthritis), which can cause: Joint pain. Swelling. Warmth. Stiffness. Loss of motion. JIA may last a few months or years, or it may be a lifelong disease.

What is osteonecrosis? Your bones are made up of living cells that need a blood supply to stay healthy. In osteonecrosis, blood flow to part of a bone is reduced. This causes death of bone tissue, and the bone can eventually break down and the joint will collapse. Osteonecrosis can happen to any bone, but most often it develops in the ends of long bones, such as the: Thigh bone. Upper arm bone. Less often, the bones of the elbows, ankles, feet, wrists, and hands are affected. When the disease involves part of a bone in a joint, it can

What is spinal stenosis? Spinal stenosis happens when the spaces in the spine narrow and create pressure on the spinal cord and nerve roots. The spinal cord is a bundle of nerves that comes out of the base of the brain and runs down the center of the spine. The nerve roots branch out from the cord. In spinal stenosis, the narrowing usually occurs over time.

What is rosacea? Rosacea is a long-term skin condition that causes reddened skin and a rash, usually on the nose and cheeks. It may also cause eye problems.

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.