Dupuytren's contracture is a condition in which one or more fingers become permanently bent in a flexed position. It usually begins as small, hard nodules just under the skin of the palm, then worsens over time until the fingers can no longer be straightened. While typically not painful, some aching or itching may be present. The ring finger followed by the little and middle fingers are most commonly affected.The condition can interfere with preparing food, writing, and other activities.

Source : Wikipedia

It was first described in 1833, and affects many millions worldwide - mostly males over 50. It involves the formation of abnormal connective tissue in the palm, and in severe cases means that the associated finger is unusable.

The cause is unknown.

Further details British Society for Surgery of the Hand

Note: There is a similar condition - called Ledderhose's disease which affect the feet. The cause is also unknown.