okay well welcome to another MedCram calm board vitals question this one
comes from the USMLE step one and comlex part one banks a 26 year old male
developed worsening weakness in his legs for the last five months he noticed that
running and walking was becoming increasingly difficult he does not have
any chronic diseases and has not sustained any injuries to his body
deficiency of which of the following enzymes is most likely you've got a
glycogen synthase be the branching enzyme see branching enzyme D acid
multis or e glucose-6-phosphatase so you know what they're looking for here
they're looking for basically do you understand your glycogen storage disease
so let's take a look here at the glycogen storage diseases so I've got
them listed there's about 8 of them actually there's 9 if you can count the
0 each glycogen storage disease is a problem with an enzyme in the process of
making the glycogen and specifically storing it so there's only one that's
actually for making glycogen and all the other ones are storing it so what
happens is the glycogen accumulates in the liver and it can accumulate in
different compartments and that causes different problems interestingly type 0
which is very rare is a problem with actually making it and so what happens
is that the liver is actually pretty small in these cases and it's actually
quite mild but all of the other ones that you would be testing on is 1
through 8 let's go through those so there's von Gierke which is a problem
with glucose-6-phosphatase and this is pretty severe they usually have problems
very early in life there's liver enlargement because of the storage of
the glycogen and the glucose is very very low
pretty severely low so these people have problems very early on that's one of the
things that you'll see with von gierek's disease pompes disease which I have here
in red is a problem with maltase and it's an alpha 1-4 alpha 1 6 glucoside
ace and the key to remember what this is it is number 2 and there are two types
there's a pediatric and there's an adult type the pediatric is pretty severe and
they're usually dead by 2 from cart my op a--they and all organs are
affected because of this with the adult however there is less of a deficiency
and they actually do fine up until later in life maybe 20s or 30s and what they
start to get is lower extremity weakness which sounds familiar here right so
there's less of an accumulation and what you'll see is you'll see these lysosomes
in the cells that are full of this stuff so lysosomal accumulation is key for
pompes disease which is type 2 and remember there are two types of the type
two there's pediatric and adult Cory is the debranching enzyme it's a milder
form of type one whereas anderson is a branching enzyme that's very severe so
think of the branching as severe and the d branching is not so severe I don't
know if it'll be helpful to memorize ml o 1/6 glucose I days for the debranching
or alpha one for alpha one six for the branching but you may need to know these
although Corey and Anderson are probably not tested as often one that is however
is McArdle's disease phosphorylase you should know that they just get muscle
cramps not really weakness just some muscle cramps so we see a big diversity
here with hers it's also phosphorylase but it's a much milder form of type one
and phosphofructokinase is very similar to type v which we've got up here and
then finally phosphorylase kinase again it's like type 1 if you do have enlarged
liver you do have decrease glucose like you do in type 1 which we have here but
it's also a milder form so really the key highlights here is that you've got
to know that there's an adult form and that adult form is type 2 which has the
multis so now if we go back and look at the question we will see what we've got
is a 26 year old male with worsening weakness in his legs for the last five
months that makes us think about pompes disease and here we're seeing
that there's running and walking which is becoming increasingly difficult he
does not have any chronic diseases so this is not a patient that would fit
into for instance type 1 okay and he's not sustain any injuries to his body so
which enzyme are we looking at so the glycogen synthase
that was type-0 and that one's pretty mild they don't get liver enlargement
the debranching enzyme was actually the more milder one let's take a look at
that one again so here with the branching that's the quarry or the Amla
1:6 glucoside ace that's a milder form of type one but that's usually something
that pops up pretty early you get liver enlargement and decrease glucose we're
not seeing that with this patient then the other one which is right below that
in the answer question was branching enzyme and typically we're seeing
cirrhosis by the age of two that's clearly not the question stem that we're
seeing so the next one is this acid multis which is of course the alpha 1-4
alpha one six glucoside ace and that's the pompey's that's the pediatric and
adult onset and that does go along with this at least the the 26-year old male
part does what about glucose-6-phosphatase let's take a look
at that 1:6 phosphatase the glucose-6-phosphatase here that one's
going to cause liver and largeman and severe decrease glucose so after we look
at all of these the one that makes the most sense is D which is the acid multis
and again what is it that you need to know you need to know the enzymes that
are involved you need to know the clinical syndromes that are involved and
I would not focus on the syndromes that are very similar to each other which
there are a lot of what I would focus on are the things that are very unique and
of course Pompey is probably out of those the one that is the most severe
that you would see an adult and of course they're going to probably test
you on that because they're going to want to make sure that you can identify
that so the right answer here is D acid multis thanks for joining us