Unique skin findings in a case of the A3 pulley trigger finger due to an osteochondroma.

Trigger finger is usually caused by stenosing tenosynovitis and hypertrophy of the retinacular sheath, and the most common site of tendon triggering is the A1 pulley. Although the A3 pulley trigger finger has been described in a few cases caused by hypertrophy of the retinacular sheath and ganglion, associated skin findings have not been reported to date. Herein, we report a rare case of the A3 pulley trigger finger due to osteochondroma with unique skin findings in a 50-year-old woman. In this case, we observed a V-shaped skin depression on the palmar side of the proximal interphalangeal joint of the right middle finger during finger locking. Additionally, we observed bilateral linear skin depressions on the sides of the proximal phalange. These findings might be caused by the traction force on the A3 pulley, connected to the skin via the Grayson and Cleland ligaments, which are fibrous tissues that connect the skin and tendon sheath.