Excerpt from Digital Mucous Cyst

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Background

Digital mucous cysts (DMCs) are benign ganglion cysts of the digits, typically located at the distal interphalangeal (DIP) joints or in the proximal nail fold. They usually occur on the hands, although they have also been noted on the toes. The etiology of these cysts is uncertain but may involve mucoid degeneration. Often, these cysts are asymptomatic and do not require treatment. When treatment is indicated, medical therapies and surgical interventions of varying magnitudes may be attempted. Recurrence is common.

Historically, little attention has been directed at studying these cysts despite their frequency. In the literature, they have been referred to as cystomata, myxomatous cutaneous cysts, myxomatous degenerative cysts, periarticular fibromas, synovial lesions of the skin, periungual ganglions, mucous cysts, myxoid cysts, synovial cysts, dorsal cysts, nail cysts, cystic nodules, digital mucoid cysts, digital myxoid cysts, and digital mucinous pseudocysts.

Hippocrates first appreciated ganglion cysts, describing a knot of tissue full of fluid. In 1746, Eller concluded that ganglia formed from the herniation of the synovial lining of a joint. In 1882, Hyde first described the DMC. In 1893, Ledderhose suggested that ganglia arose spontaneously in the subcutaneous tissue. In 1895, Ritschel proposed the earliest formulation of the theory that mucoid degeneration may be responsible for DMCs; Carp and Stout popularized the theory in 1928. Then, in 1947, Anderson reported that cysts caused the nail deformities.

Pathophysiology

The mechanism of formation of DMCs is unknown. Currently, it is believed that the cysts arise from mucoid degeneration of connective tissue and that this process, in most cases, involves communication with the adjacent DIP joint and possible coexistence of osteoarthritis. Clinical and radiographic evidence of osteoarthritis is common at the site of the cysts, and the frequent presence of osteophytes and spurring of the DIP joint were recognized in the 1970s. Active connection to the joint space may or may not exist, as the mucoblasts associated with the cyst appear capable of sustaining the process.

Frequency

United States

Ganglia are the most common tumor or cyst of the hand. They account for approximately 70% of all such tumors or cysts, with DMCs comprising 10-15% of the total.

International

Frequency data are limited but not significantly different from US statistics.

Mortality/Morbidity

DMCs most often are asymptomatic and benign. Pain can result from the impingement of cysts on adjacent nerve fibers. Larger cysts can disfigure the affected digit. Nail deformities can occur.

Sex

Women are affected more often than men (female-to-male ratio of 2-2.5:1).

Age

DMCs usually occur in the fifth to seventh decades, yet they may be seen as early as the teenage years or among the elderly population. The mean age of onset is 60 years. One report describes a case in association with cutaneous mucinosis of infancy.

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