all right so here we're going to continue our discussion on the lysosomal storage disorders and here we're going to go over the muco polysaccharidoses now the nice thing about this is that there's no biochemical pathway that you need to memorize unlike the sphingolipidoses where you've got a biochemical pathway you've got to memorize a lot of different enzymes you gotta remember uh the products that build up and then there's six or seven diseases that you need to be aware of for this there's only two there's no biochemical pathway that you need to remember for the most part you need to understand the manifestations of these disorders how to distinguish the two the enzymes that are involved and that's pretty much it so this is fairly straightforward stuff here now there are two disorders hurler syndrome and hunter syndrome they have a lot in common the major differences are what the usmle is going to hammer on so before we go over these disorders let's just briefly talk about what muco polysaccharides are mucopolysaccharides are also known as glycosaminoglycans there are several of them but what they really are are very highly polar polysaccharides that exist within connective tissue so we're talking bone and cartilage and the connective tissue on heart valves and so when these are uh when they build up they cause defects of those tissues uh and so that's really where the manifestations are going to be so first of all what do hurler and hunter syndrome have in common well the major thing is these uh the this facial i don't know if you want to call it a defect but uh this these facial manifestations that show up in children and this is called gargoylism now gargoylism is kind of an outdated term but i included it here because it kind of helps you remember how this looks now another way to think of it is that the facial appearance of these patients bears a striking resemblance to the facial appearance of adults who have acromegaly now it's a complete that's a completely different disorder with a com very very different uh pathophysiology but the appearance is pretty similar so we're talking here about frontal bossing we're talking about very prominent facial bones uh there's a flattened nasal bridge hypertelorism and macroglossia or an enlarged tongue so some of those things you see in acromegaly and you'll see this in a child gradually developing although it can be present at birth but developing over the course of childhood now we would not see acromegaly in children we would see that in adults but you see some of some of the similar features now another thing that you're going to see that these two have in common is the collection of mucopolysaccharides because we're unable to degrade them and so those mucopolysaccharides are chiefly heparin sulfate and dermaton sulfate so those are the two things that these disorders have in common now what is different well for hurler syndrome it's a little bit more severe as far as the gargoylism goes they're going to have also corneal clouding now that's just due to the fact that in the cornea are mucopolysaccharides so because it's a little bit more severe they have ocular manifestations you can also get hepatosplenomegaly with hurler syndrome and because of the more severe facial issues you can get airway obstruction the enzyme that's deficient in hurler syndrome is called alpha l-idiodase and the way i remember this is simply that hurler syndrome has an l in it and so does alpha l in uranidase hurler syndrome is inherited in an autosomal recessive fashion we're gonna see that that's different from hunter syndrome now hunter syndrome is really just a mild version of hurler syndrome so you'll see that gargoylism but it may be a little less prominent what you'll really see with hunter syndrome is that gargoylism but also aggressive behavior and we're not exactly sure why that happens but they tend to have aggressive behavior what they don't have is that corneal clouding so the way that people tend to remember that is that hunters are often men and so it's x-linked and so that will tend to be in boyce hunters have to be able to see their target and so they don't have corneal clouding and hunters shoot and that's kind of an aggressive action right so that's hunter syndrome and so really that's it hurler syndrome and hunter syndrome those are the two muco polysaccharidoses remember that heparin sulfate and dermatan sulfate which are mucopolysaccharides will accumulate and then remember that hurler syndrome and hunter syndrome both have gargoylism which looks a lot like acromegaly in the face hurler syndrome will have corneal clouding and hepatosplenomegaly whereas hunter syndrome will have normal but aggressive behavior and that's really it for the mucopolysaccharidosis [Music] foreign