What is syphilis?

- [Voiceover] Syphilis is a fascinating sexually transmitted infection. It's caused by a bacterium referred to as treponema pallidum, treponema pallidum. It's part of this genus of bacteria referred to as treponem, sometimes you'll hear it referred to as a treponem, or it can also be referred to as a spirochete. A spirochete, which is the name for a group of bacteria that literally look like a spiral. So it looks like this when you inspect a sample that's been infected with syphilis under a microscope, and we'll talk more about that in a separate video. And what makes syphilis very interesting today, so I'll put spirochete on my Y axis, and I'll make time our X axis. We'll see that syphilis dropped over the years, until about the year 2000, when it actually started going up again. So I'll label right here as about 2000. So the rate of syphilis infection has been increasing slowly in recent years. And the group that's seen the greatest rise in incidents, are men who have sex with men. So let's take a better look at syphilis, and figure out how it's spread from one person to another. And as you might recall, this process is referred to as transmission, so a sexually transmitted infection is transmitted from one person to another. And of course with an STI, the most common mode of transmission is sex. That includes oral sex, vaginal sex, and anal sex. And childbirth is a very important mechanism of transmission as well. Now the interesting thing about syphilis is that it can only live within the cells of human beings. Which means that if we cured everyone on the planet that had syphilis, we could effectively eradicate the disease. But the trick with syphilis is identifying it when it occurs. Sir William Osler, the person who many consider to be the father of modern medicine, called syphilis "the great imitator", because it can masquerade as a variety of different disorders. And we'll talk about why that is in a minute, but the trick with syphilis is to try and identify what stage a person is infected with. So let's go through the different stages. Starting with the point when a person is infected, it will take about three weeks. So I'll write here three weeks. So three weeks before they show any symptoms. And this first stage in which they begin to show symptoms is referred to as primary syphilis, primary syphilis. So with primary syphilis, the majority of your symptoms will occur at the site of contact, or where the infection is directly spread to. That means that the organs initially affected will be your genital organs. So let's take a look at our friend right here, this poor guy that's going to have all the different signs and symptoms of syphilis. So let's take a look at a zoom-in of his genital organs. Primary syphilis will have two main features. The most classic thing, and I'll abbreviate right here, primary syphilis, so the first of the two classic things you'll see, is what's referred to as a chancre, a chancre, which just means a lesion that can occur on the shaft or on the tip of the penis. In a female, this would occur on the cervix. And it's a fairly gruesome looking ulcer, it's very indurated, and so you'll see these edges right here, so I'm trying to imply that it's a very deep, indurated lesion. Which looks bad, but the interesting thing about the chancre, is that it's painless. Which is an important distinction to make between syphilis and another STI referred to as chancroid. Where you'd see a chancre, but this one will definitely be painful. The other thing you might see is what's referred to as a lymphadenopathy, lymphadenopathy, or LAD. And that just means that the lymph nodes that you have, commonly the regional ones located near the genital tract. So the inguinal lymph nodes that are along the crease, here along the waistline, they're going to be larger. And they may even be painful. So you'll have inguinal lymphadenopathy. So this lymphadenopathy and the chancre tend to heal in about three to six weeks, whether you give this person treatment or not. And after that they'll further progress, over the course of about nine weeks, to secondary syphilis, secondary syphilis, and I'll just write secondary for now. Now with secondary syphilis, this spirochete spreads from the genital tract to the bloodstream. And starts to cause more systemic symptoms, so symptoms you see elsewhere than just in the genitals. And because white blood cells will go chasing after syphilis in secondary syphilis, so this is how I'll abbreviate secondary syphilis right here. One of the first things you might see in secondary syphilis because of the white blood cells attacking the treponem, is fever, and if you take a look down here, I've drawn a blood vessel where you've got the endothelial cells that line a blood vessel over here, drawn out, so let's say that the treponem seeds into a blood vessel here, and one of the characteristic things about syphilis is that it likes to invade these endothelial cells. And so you might see them inside here. Now, white blood cells will respond to this infection, and attack syphilis with a vengeance. And they'll do this by swallowing up the syphilis. They can also cause cell death for the infected endothelial cells, through a process called apoptosis, or they'll release these compounds into the bloodstream, these cytokines that are supposed to signal to the body that it's under attack. And these compounds are called cytokines. So I'll label right here, these are cytokines, that will, to a certain extent, tell cells what to do, so cytokines can trigger cells to undergo apoptosis and die. But they can also travel through the bloodstream, and up here, to the brain, where they can signal the brain to raise the body temperature, resulting in a fever. And this is one of the classic features that occurs when white blood cells are attacking some invading pathogen, all under this process referred to as inflammation. Another result of that can include more lymphadenopathy, so you'll have swelling at the lymph nodes that may occur regionally, or even elsewhere in the body. But more locally with secondary syphilis at the genitals now instead of the painless chancre, we may start to see these large warts known as condyloma lata. Or if you're referring to a single one of these warty lesions, you can refer to them as a condylomata latum. So this looks like a large white wart, that likes to form on mucous membranes. Which means the tip of the penis, or the cervix, or the vaginal wall in a woman, or even on the inside of the mouth. And what these represent are the syphilis bacteria that are actively fighting the white blood cells that are there. And these tend to be painless as well. And finally, one of the last classic symptoms you'll see with secondary syphilis, is this very characteristic skin rash that's referred to as a maculo, so maculo meaning just flat, maculopapular. Which means, ironically, raised. So either a flat or a raised rash. A maculopapular rash that occurs all over the body, as you'll see down here. But one of the things that makes this rash very unique to syphilis, is that it'll appear on your palms, and even the soles of your feet. Which is something that very few diseases can do. Usually rashes will occur elsewhere in the body, all over anywhere, but not on your palms or your soles. That actually cuts down the differential diagnosis to a few things. And keep in mind, it's not going to be just a single lesion that characterizes this rash. You're going to see a bunch of these occurring on your palms, your soles, your arms, your belly, all over. And this just represents the treponem spreading to the layers of your skin, and the white blood cells that are fighting them. So they're essentially a result of inflammation as well. All right, so after secondary syphilis, these symptoms will go away, and they'll take also about three to six weeks to heal. And within two years of this initial infection, we'll arrive at a stage referred to as early latent syphilis. Early latent syphilis. And when we say that syphilis has become latent, that indicates that we have no symptoms. So there are no symptoms, and I'll abbreviate symptoms as SX. The same holds true for the next stage of syphilis, which is referred to as late latent syphilis. So here too we have no symptoms. But the other difference are that early latent syphilis is more likely to have a relapse of symptoms. So more likely to relapse, but also, early latent syphilis is more contagious than late latent syphilis. And these two points make sense because early latent syphilis is closer in time to the point when we had our initial infection, because it happens within two years. Whereas late latent syphilis will occur after two years. So after two years of the initial infection. So if we're at the two year and one day mark after we've had our initial infection, and we don't have symptoms anymore, that means we are in late latent syphilis.