I was told when I was first diagnosied that it was only from Scottish and Irish ancestry. My doctor was not aware of any other area being affected.

Somewhere down below this thread is another posted
by a person (Sinjay?) who stated that to the best of
his knowledge he was of Indian descent with no non-Asian
lineage; and, he has DD/DC. On the Dave's Dupuytren site
there is a link to "Dupuytrens from a Historical Perspective." Dr. Adrian Flatt describes the condition and
statistics in various parts of the world. It is a few pages
in length and, I think, worth a read. Dr. Flatt also has
DD. If I recall correctly, DD/DC does exist outside of
Eupopean Poulations, but with comparatively low penetrance.
If Danes have a 30% penetrance, Blacks and Asians may have
3-5% or some similar comparison. Conceiveably, there might
be some unknown details in the family history. Please do
not use my Dane/Black, Asian numbers as accurate. Read the
article first hand.

Miriam,

It's a case of heredity. If you had no inflicted trauma then you and your siblings most probably inherited the ailment from both parents.
One progenitor may have had at least a dominant gene or both.

Your sister may resemble the iceman or the milkman. (Kidding of course)

Those Vikings were up to no good.