> To that end, I'd like to ask about the cpk test. I've read
> conflicting views on the levels. Some have said that higher levels
> mean more muscle damage and others say this to be untrue. I know
I've also read that the number is very low at "end stages" . What's
the scoop?

CK (or CPK) is a muscle enzyme which leaks into the bloodstream when
muscles are damaged. This can be caused by MD, although there are
many other possible causes as well. Among the forms of MD which
typically show very high levels of CK are dystrophin deficiency
(Duchenne MD/Becker MD), sarcoglycan deficiencies (Limb girdle MD
types 2C, 2D, 2E, and 2F) and dysferlin deficiency (LGMD type
2B/Miyoshi myopathy) Because most of these types of MD tend to show
fairly rapid progression, it seems like a lot of people seem to make
the association between higher CK levels and more severe disease.

Dysferlin deficiency is an exception to this rule, it has very high CK
levels but a slow progression. Probably the common denominator is
that the sarcoglycans and dysferlin form part of the cell membrane of
muscle fibers (so it makes sense that the membrane would be easily
damaged if it's missing one of these) while dystrophin is indirectly
attached to the cell membrane.

the drop in CK in the "end stages" refers to patients who have very
little muscle left in their bodies, so there's not much muscle to leak
out CK. This phenomenon doesn't appear to be relevant to dysferlin
deficiency, since patients retain a fair amount of muscle function for
decades after symptoms first appear.

So probably CK tends to get overplayed. It's a good clinical
indication that there is a problem in the muscles, but it isn't
specific to MD, or to a particular type of MD. ALthough there may be
some disagreement about this, the CK level probably shouldn't be taken
as a quantitative measure of how the muscles are doing.