Digital mucous cyst are most common in people who have arthritis on the fingers.
A digital mucous cyst, also called a myxoid cyst, is a smooth, shiny bump that grows at the base of and under the fingernail. This often forms a groove on the nail that is several millimeters wide. The cyst is filled with light yellow to light pink jelly-like sticky fluid. Most digital mucous cysts are harmless, but if unattended to, can become inflamed, red, swollen, and painful.
Digital mucous cysts form when the connective tissue in the joint space is broken down, creating an opening between the joint space and the skin. Joint fluid and other joint debris then form the jelly-like material that fills the space.
A digital mucous cyst is best treated by one of the following approaches:
- Surgical drainage of the cyst contents using a sterile needle.
- Injection of steroids into the cyst to decrease inflammation.
- Injection of hyaluronidase (an enzyme that can break down the cyst’s contents) into the cyst.
- Injection of a sclerosing agent (medical detergent) to destroy the cyst. This is typically done after the cyst contents have been drained.
- Cryotherapy, or freezing the cyst using liquid nitrogen.
- Surgically removing the cyst.
- Surgically removing the bone spurs and joint space debris associated with arthritis to prevent the cyst from reforming.