Youtor
USMLE MSK 2 Bone Pathology and Pharm Osteoporosis and More
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Want to support the channel? Be a patron at: • / lymed Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day. • Follow along with First Aid, or with my notes which can be found here: https://www.dropbox.com/sh/ces0j7obod... • We just finished our discussion on bone formation, now we'll move on to bone pathology. We start with achondroplasia, a genetic mutation that affects cartilage and thus bone formation. This results in dwarfism. • We then move on to osteogenesis imperfecta, which is again a defect in cartilage production. Thus bone formation is affected. Other common signs include blue sclera and deafness. • Those are some congenital defects in bone formation. But even if you don't have those, you can have problems with bone formation. For example, if you have poor vitamin D intake, then you can have pathologies such as osteomalacia or rickets. Some signs of rickets include genu varus, genu valgum, and rachitic rosary. We will also discuss important lab findings of rickets (as well as others). We will also discuss the role PTH may play in bone development. For example, too much PTH may cause osteitis fibrosa cystica and cystic holes in your bones. • Our next topic is osteoporosis. This is decreased bone mass and is very common. For that reason, we like to screen patients when they're older with a DEXA scan. Lab findings are often normal, but due to decreased bone mass, there can be pathological fractures. Now old age isn't the only thing that causes osteoperosis. Other causes include drugs like PPI, anorexia and amenorrhea, and lack of exercise. Pharm for this includes bisphosphonates, PTH analogues, hormone replacement, SERMs, and danosumab. As always, we will discuss the mechanisms and side effects. • Those are all conditions in which we have bone loss or impaired bone formation. But there are some conditions where we have INCREASED bone. One of these include osteoPETROSIS. This is due to a defect in carbonic anhydrase which may impair the ability of acid to break down bone. If this is impaired, then you have uncontrolled bone formation. However this bone is fragile and can invade into your bone marrow causing pancytopenia. They can also impinge nerves. Labs may show minimal lab changes or decreased calcium. • Next one is Pagets Disease. This is disorderly bone formation. You have different stages of bone formation but the result is thickened bone. We talk about common presenting symptoms and how they like to ask it on the USMLE. • That does it for the making and breaking down of bones. Let's move on to bone infections. Bone infections are called osteomyelitis. There are many pathogens that will be in my note. • The last topic for today is osteonecrosis or death of bone cells. It's common in locations like the femoral head due to retrograde blood supply.
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