Leucism is not the same as neural crest defects but can include some forms of neural crest defects as causes of leucism though there are also other causes of leucism which is hypopigmentation. Hypo means "below" (like in hypodermic which means below the skin) or "less" (like in hypothermic which means cooler than the body is supposed to be, so less heat) and pigmentation is coloring. Okay, I will make it short and sweet -- only the basics. The embryo in the beginning is only a clump of cells that are all the same. Those are stem cells. There are not organs, and the shape is just a clump. The next shape once there are enough cells looks like a soccer ball and is hollow like one, too. There are still no organs. Eventually, there are more cells but still no organs. Once there are enough cells they start to have some differences (again, no organs and no human shape yet). The different areas are called "crests". The cells then are no longer true stem cells because they can not grow into absolutely anything. One of the earliest crests in the cardiac neural crest: http://en.wikipedia.org/wiki/Cardiac_neural_crest_complex and like it sounds, the cells from that will create things like the heart and nerves but also a lot more, including pigment cells and part of the structure of the jaw and ears. Later the cardiac neural crest differentiates into two crests: the cardiac crest and the neural crest. The neural crest controls the formation of many things so when you have a mutation there a wide range of things can go wrong in many parts of the body: the individual may be deaf or partly deaf, the nerves for the GI tract may be wrong which creates a lot of problems down the line, the jaw may not work properly, cardiomyopathy rates are increased (which is thought to perhaps be due to damage to the sympathetic nervous system), and other things can also go wrong at higher rates than for individuals who do not have those genetic variations. Here is the wikipedia section on it: http://en.wikipedia.org/wiki/Neural_crest Yes, it is a somewhat complicated topic, but ferret people get used to complicated topics. Heck, we have animals who are prone to endocrinological diseases like adrenal disease and insulinoma, so we have to get used to complex issues. Never thought you'd wind up learning so much biology just from loving a weasel, right? LOL! Sukie (not a vet) Recommended ferret health links: http://pets.groups.yahoo.com/group/ferrethealth/ http://ferrethealth.org/archive/ http://www.afip.org/ferrets/index.html http://www.miamiferret.org/ http://www.ferrethealth.msu.edu/ http://www.ferretcongress.org/ http://www.trifl.org/index.shtml http://homepage.mac.com/sukie/sukiesferretlinks.html all ferret topics: http://listserv.ferretmailinglist.org/archives/ferret-search.html "All hail the procrastinators for they shall rule the world tomorrow." (2010, Steve Crandall) On change for its own sake: "You can go really fast if you just jump off the cliff." (2010, Steve Crandall) [Posted in FML 7095]