I thought I’d put together a slide that covers some of the main autosomal recessive disorders
that you’ll be responsible for knowing. You don’t necessarily need to know all of the details about them
but you do need to able to recognize them as autosomal recessive. First of all, sickle cell anemia.
I think we’ve covered that plenty and you probably understand mostly about that. We just covered
cystic fibrosis as a great example of an autosomal recessive disorder where we’re thickening the mucus
because of a broken chloride transporter. Albinism, that one’s pretty self-explanatory. All pigmented
areas end up white or unpigmented. Then phenylketonuria, you’ve probably heard of. But children,
when they’re born get a foot prick to take a blood sample. The testing for this has been around
for a long, long time probably since the 40s. What this is is it causes a build-up of phenylalanine.
It causes that to be in the urine but phenylalanine turns out to be really toxic in high doses.
So phenylalanine doesn’t get converted to tryptophan. So, if we have a big build-up of that,
it’s a problem. But one of these conditions, if you test for it, very easy to treat. You can remove
the phenylalanine which is found in things like diet Coke and most proteins unfortunately.
But that will end up not causing the mental retardation that would come about
if there was a build-up of phenylalanine. Tay-sachs disease is a hexosaminidase A deficiency
which means that the lysosomal storage, basically the trash lysosomes that are inside the cells
end up getting packed with trash and not broken down. So, hexosaminidase A is what will break things down
in order for them to be disposed of. Tay-sachs disease is a really sad and it ends up being a fatal disorder.
It’s not treatable at this time. Hemochromatosis, we’ve already covered. Then there are a number of
different glycogen storage deficiencies that also are autosomal recessive disorders. Tay-sachs disease
falls under lysosomal storage diseases. There are other lysosomal storage diseases. You don’t necessarily
need to know them all by name. But again, you should know them as homozygous recessive disorders
or autosomal recessive disorders. Keep these ones in mind because they are important to know.
Now, you’re going to run into a vast number of different disorders. This is a hint that I’ve always sort of gone by
is that almost all diseases that make an appearance during childhood will be autosomal recessive disorders.
The way that I will think of that is it’s easier to remember this fairly short list of autosomal recessive disorders
than it is to remember all of the other disorders. So if you can keep those ones in mind, you’ll be in great shape
because then you can get a question that perhaps says, “Oh, what is this?” And you don’t have it
on your list of autosomal recessive. You can guess it as an autosomal dominant disorder
or perhaps even more of X-linked type of disorder anyway, so a little hint for you there.