A digital mucous cyst is a common, benign lesion that presents as a firm nodule on the fingers or toes. The lesions are usually not painful and are found near the distal joints. They typically appear smooth or shiny with an almost translucent appearance and an average size of 5-8 mm (roughly the size of a pencil eraser). Digital mucous cysts are found in a wide range of ages from teenagers to the elderly, but are most likely to occur during the 7th decade. They are similar in nature to ganglion or synovial cysts which are often found on wrists or behind knees.
There are currently two accepted forms of digital mucous cysts. The first is an extension or herniation of the lining of the adjacent joint. This form contains a fluid that is found within the joint itself and can be related to trauma, arthritis, or can occur spontaneously. The second consists of a deposit of a gelatinous substance called mucin and is not connected to the joint space. When these lesions appear near the base of the fingernail/toenail, they may cause grooving or splitting of the nail and occasionally complete or partial nail loss. When ruptured, these cysts drain a clear, thickened, jelly-like substance.
Digital mucous cysts may resolve on their own, however, a large percentage will require evaluation and treatment by a dermatologist. The most definitive treatment for digital mucous cysts is surgical excision and fusion of any communication with the underlying joint. This procedure provides over a 90% cure rate, although recurrences are not uncommon. Other treatment options include cryotherapy, CO2 ablative laser, and repeated sterile drainings. All treatment of digital mucous cysts should be performed by a physician in order to avoid possible complications including joint infections and permanent damage to the affected fingers or toes. A biopsy may also be performed to rule out other rare conditions that may involve certain health risks if left undiagnosed.
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