A myxoid cyst, also known as a digital mucous cyst, is a small, fluid-filled, benign lump. These cysts commonly form near a joint at the end of a finger or toe, often close to the nail. While generally harmless, they can sometimes cause discomfort or interfere with daily activities.
Understanding Myxoid Cysts
Myxoid cysts typically appear as smooth, shiny, translucent bumps. Their color can range from flesh-toned to reddish or bluish. These cysts usually measure between 5 millimeters and 1 centimeter across.
The bumps contain a jelly-like fluid, often a type of mucus or synovial fluid. If the skin over the cyst breaks, this fluid may leak out, sometimes appearing clear, yellowish, or slightly pink. Myxoid cysts most frequently develop near the nail on the index, middle, or ring finger of the dominant hand, though they can also occur on the toes. These growths are benign. They are sometimes referred to as pseudocysts because they do not have a true surrounding capsule like some other cyst types.
Causes and Risk Factors
The cause of myxoid cysts is not always clear, but they appear related to a weakening or degeneration of connective tissue. A common association is with degenerative joint disease, such as osteoarthritis, in the adjacent joint. Some myxoid cysts are considered a type of ganglion cyst that connects back to the joint lining.
Another suspected origin involves abnormal deposits of mucin, a component of mucus, within the skin itself, which may not be linked to joint degeneration. Myxoid cysts are more frequently observed in middle-aged and older adults. They are also more common in females, affecting them up to three times more often than males. Many individuals with osteoarthritis also develop myxoid cysts. Trauma or repeated small injuries to the finger or toe may also contribute to their development.
Recognizing and Addressing Myxoid Cysts
Myxoid cysts can present with various symptoms. While often painless, they may cause discomfort or tenderness, especially if they press on nearby nerves or if underlying arthritis is present. Pressure from a cyst growing near the nail matrix can lead to changes in the nail itself, such as grooving, depressions, alterations in color, or even splitting and loss of the nail. If a cyst ruptures, it may leak a clear, yellowish, or sometimes blood-tinged fluid, and carries a risk of infection.
Diagnosis is typically made through a physical examination. During this examination, the doctor may ask about the cyst’s growth, pain, color changes, or recent trauma. Imaging techniques like X-rays may be used to assess for signs of osteoarthritis in the joint, and an ultrasound can help visualize the cyst. In certain cases, a biopsy might be performed to rule out other conditions.
Treatment varies based on the cyst’s size, location, and symptoms. If a cyst is small and not bothersome, observation may be recommended, as some can resolve on their own.
Conservative Treatments
Conservative treatments include aspiration, where a needle is used to drain the fluid. This procedure often needs to be repeated, and recurrence rates can be high. Another conservative approach involves draining the cyst followed by a corticosteroid injection to help shrink it, though this can sometimes thin the skin. Cryotherapy, which involves freezing the cyst with liquid nitrogen after draining, is another option to prevent fluid re-accumulation. Laser ablation using a CO2 laser to remove the cyst base after draining is also a possibility. Applying repeated firm pressure to the cyst has also been used to encourage its disappearance.
Surgical Removal
For cysts that are persistent, painful, or causing significant nail deformity, surgical removal may be considered. This procedure is often considered the most effective, with high success rates. Surgical removal involves removing the cyst and may include sealing any fluid leaks from the joint. The procedure might also involve scraping the joint and removing bony outgrowths (osteophytes). While recurrence is possible with all treatment methods, surgical removal generally has the lowest recurrence rates. Potential side effects of various treatments can include scarring, pain, swelling, or a reduced range of motion in the affected joint.