Background: \- The rare disease melorheostosis causes bones to thicken. This may lead to pain, and can affect bones, joints, and muscles. Researchers want to learn more about the disease and how it progresses.

Objective: -To see what happens to people with melorheostosis over time and understand the causes of the disease.

Eligibility: * People 18 and over with melorheostosis. * Their unaffected relatives.

Design: * All participants will have a medical history and physical exam. * Participants who are relatives will give samples of blood or cheek cells. * Other participants will be in the study for about 1 week. * They will have blood and urine collected. * Strength, walking, and range of motion will be measured. * Participants may also have * X-rays and scans. * A pain and neurological evaluation. * Their skin evaluated by a dermatologist. * A small sample of bone taken. * Nerve conduction studies. Small electrodes with to wires will be put on the skin. A metal probe will give a small electrical shock. * Electromyography. A thin needle will be placed into the muscles. * An ultrasound, which uses sound waves to examine the muscles and nerves. An ultrasound probe will be placed over the skin. * A bone scan. They will get a small amount of radioactive fluid through a needle in an arm vein. This fluid travels to the bones. The bones will be photographed in a machine. * Bone Densitometry, a low-level x-ray. * Photographs taken. * A small circle of skin removed with a surgical instrument. * Questionnaires about their quality of life. * Participants will be asked to return about every 2 years. At these visits, participants may have blood and urine tests and x-rays.