myxoid cyst (mucous cyst, digital myxoid pseudocyst)

Introduction

Digital myxoid pseudocyst.

Etiology

• unknown
• often associated with Heberden's node in patients with osteoarthritis
• less commonly associated with chronic irritation, ill-fitting shoes

Epidemiology

• generally occurs in the elderly (> 60 years of age)

Pathology

• cyst associated with extension of joint's synovial lining
• pseudocyst resulting from the leakage of join mucin into the surrounding skin

Clinical manifestations

• generally solitary cyst
• rubbery & translucent in character
• occurs on dorsal aspect of distal interphalangeal joint on finger, less commonly on toe
• occurs at the base of a fingernail or toenail
• cystic appearance & transillumination
• clear gelatinous fluid may be exuded from opening
• when a myxoid cyst is over the nail matrix, nail plate dystrophy occurs

Management

• firm compression daily over a period of weeks
• due oto the possiblity of communication with the joint space, excision, cryotherapy or intralesional glucorticoid should be performed only by physicians experienced in treating these lesions

More general terms

• synovial cyst
• pseudocyst