Collagen Related Diseases And Odd Facts About Guinea Pigs

I'm studying for my block II exam. It's not a disease course, but we are expected to know the diseases that arise from different molecular etiologies.

There are quite a few diseases having to do with collagen defects.

• Osteogenesis imperfecta aka Brittle Bone Disease or Lobstein syndrome results from a mutation in collagen type I that substitutes another amino acid for glycine (which is the simplest, smallest amino acid), and as a result the triplet of alpha helices which make up collagen cannot pack as tightly.
• Ehlers-Danlos syndrome can manifest in many different forms. The host of possible problems include abnormally flexible joints, loose joints, abnormally stretchy skin, fragile skin and blood vessels and poor wound healing.
• Dystrophic epidermolysis bullosa involves a mutation in collagen type VII, the anchoring type of collagen, which links the basement membrane of the epidermis to the fibrillar collagens in the dermis. There is a recessive and dominant form. The disease causes severe blistering and skin wounds heal extremely slowly.

As far as I can tell OI, EDS and DEB all affect both dogs and humans. I'm not sure about other species.
Note: Epidermolysis bullosa simplex is a disease of cattle (and humans) that involves a mutation in keratin 5. Keratin is an intermediate filament, not a collagen.

Scurvy is a disease that is caused by a deficiency of vitamin C. Humans get this disease because they cannot synthesize their own vitamin C. Vitamin C is a co-factor required for the hydroxylation of prolines and lysines on the alpha helices of collagen. Without hydroxylation, the alpha helices don't form the triplet superstructure of which collagen is composed and so you can't make collagen. This results in problems any place in the body that needs new collagen formation-- hence the resulting clinical signs of fragile skin and blood vessels, bleeding, loose teeth and impaired wound healing.

Guinea pigs and primates are the only animals that aren't able to synthesize their own vitamin C. (I can't find anything about guinea pigs' larger South American relative, the capybara-- which is the largest rodent in the world. I wonder if they can make vitamin C?)

So here are the ood facts I know about guinea pigs so far from vet school and the clinic:

• Guinea pigs are not able to make vitamin C and so must have it supplemented in their diet.
• Guinea pigs' bronchoesophageal artery often branches off the right subclavian artery whereas in dogs and other domestic species the bronchoesophageal artery branches off the right fifth intercostal artery (yes, that was in my block I notes on embryology)
• You should not use Clavamox or other cephalosporins in guinea pigs because it will affect their gut flora (I'll never forget an exotics vet that I did an internship with back in tech school ranting about a general practice vet prescribing Clavamox for one of her cavy patients)