Stanford School of Medicine
- What is TB?
- TB epidemiology
- TB pathogenesis
- Primary and Secondary TB
- Pulmonary TB
- Extrapulmonary TB (part 1)
- Extrapulmonary TB (Part 2)
- Mantoux test (aka. PPD or TST)
- Interpreting the PPD
- Diagnosing active TB
- Preventing TB transmission
- Preventing TB using the "4 I's"
- Treatment of Active TB
- Drug-resistant TB
- TB and HIV
Learn the effects that TB has on the lungs and some important clinical clues. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Stanford School of Medicine.
Want to join the conversation?
- At9:50, what does SXS stand for?(7 votes)
- leylita is correct that "SXS" means "symptoms". Shortly thereafter the term "signs" was written. In medical terms, "symptoms" are things that a patient describes or complains of to a health care provider. Examples of "symptoms" are cough, pain, fatigue, nausea, itching, headache, etc.). "Signs" are things that a health care provider discovers by examining the patient by looking, touching, listening, feeling, smelling, etc. Examples of "signs" are blood pressure, temperature, respiratory rate, heart rate (these 4 are sometimes called "vital signs"), or sounds heard with a stethoscope or things seen by looking in the throat, ears, eyes, etc. Hope this helps.(15 votes)
- Does that conjunctivitis itch? It sure looks like it does.(6 votes)
- by the word "children," what age range does he mean?(3 votes)
- There are actually different ranges since some pediatrician I know classify those under 20 or under 18 as children too(4 votes)
- Why is pulmonary TB the most common infection?(3 votes)
- TB is transmitted through droplet and the only way it will get inside you is through your nose or mouth, so mostly TB bacteria affect the lung(4 votes)
- what if the sesitivity is 50 %(2 votes)
- Imagine you have 100 people with TB, then a test with 50% sensitivity will correctly identify 50 of them with TB and 50 other as healthy(3 votes)
- Which is the country that has the moat Tuberculosis?(2 votes)
- A WHO report from 2007 states that India got the highest total number of infections (2 millions new infections), while Swaziland had the highest numer per inhabitant (1200 per 100000 persons).(3 votes)
- Why IS the sweating most common at night?(3 votes)
- Probably because at night you are all wrapped in your blankets, even if you don't notice it.(0 votes)
- Around5:23, the physician states that weight loss is a very common symptom (though it's a sign, right?) in ANY chronic disease. That can't be true, because diabetes is associated with obesity rather than weight loss. Did he mean a chronic, INFECTIOUS disease, where the immune system consumes significant amounts of energy for activation over long periods?(1 vote)
- Yes, weight loss is a sign. Yes, not all chronic diseases result in weight loss (asthma for example). Yes, chronic infection often results in weight loss because of resources being diverted as you describe.
However, when we talk about the association between obesity and diabetes, it's important to remember that the obesity comes first and drives the diabetes, whereas weight loss comes as a consequence of chronic disease (the causality is reversed). Indeed, weight loss (rather than gain) is a key sign in the diagnosis of type 1 diabetes. The lecturer's point is that weight loss is a nonspecific sign of chronic illness and therefore whilst someone with pulmonary TB infection may well be thin, that's not sufficient to say they have TB.(2 votes)
Voiceover: I'm Charles Prober. Voiceover: And I'm Morgan Theis. Voiceover: And in this video, we're going to talk about pulmonary disease caused by tuberculosis. The reason we're dedicating a full-on video to pulmonary disease is that pulmonary disease is the most common form of clinical tuberculosis. It represents somewhere between 60 and 80% of all clinical disease attributable to tuberculosis worldwide, so it's way important. Voiceover: Okay. Voiceover: With pulmonary disease, as with any form of tuberculosis, disease may result either from a primary infection that is the first time the host is seeing the infection, and that's called primary, or it may be secondary, which results from reactivation of dormant infection or sometimes from infection from a second source in a person who had a prior infection. It's their second experience with tuberculosis. The distinction between these two is that with primary tuberculosis, pneumonia following primary tuberculosis, or pulmonary disease following primary tuberculosis is more common amongst children than adults. Children are more likely to manifest pulmonary disease with their primary infection. Then the other contrasting element is that with primary tuberculosis, the part of the lung which is involved is usually the lower lobes or the middle lobes. That's contrasted from secondary tuberculosis, where the part of the lung that's involved is usually the upper lobes. it is said that this difference results from the higher oxygen tension in the upper lobes, which I think facilitates reactivation, but I'm not sure about the mechanism, but nonethless, it is an association which has stood the test of time. From a clinical standpoint, the disease caused by tuberculosis can be the same whether it's resulting from a primary infection or from a secondary infection. The disease can be along an entire spectrum. At one end of the spectrum is mild disease with a minimal amount of symptoms attributable to the infection and at the other extreme it can be very severe with progressive lung damage, severe disability, even leading to death. Not only is there differences along that clinical spectrum, but in parallel, there are radiographic differences along the spectrum. In some occasions, pulmonary disease is associated with a small infiltrate, a small abnormality on the chest x-ray, whereas at other times the disease may be widespread throughout both lungs and may take on a cavitary appearance, which results from lung parenchymal destruction, so really across a broad spectrum. Voiceover: Okay, so with either primary or secondary pulmonary TB, you can be anywhere on this spectrum? Voiceover: Exactly. Voiceover: Okay. Voiceover: The other thing that I would say about pulmonary tuberculosis is if it is not recognized and not treated or back in the day where there was no anti-tuberculous therapy, the clinical course of disease, a so-called natural history, that is what happens if you don't treat it, was divided a third, a third, and a third. One-third of patients went on to die of their untreated pulmonary disease, and that death could often be quite rapid and it was called, back in the day, galloping consumption, consuming the person's life. That's about a third. A second third, the patients would actually spontaneously remit, they would get better. Their signs and symptoms would go away and they would then be well. Then the final third would have progressive lung involvement, not galloping, but more slow, and this was often referred to as consumption without the word galloping in front of it. That would be the natural history of tuberculosis. Voiceover: It always seems like they should just call it the natural course, instead of the natural history, but there you go. Voiceover: I think that that's a good point. Now, when you see somebody who may be infected with tuberculosis, they often have, in addition to their pulmonary signs and symptoms, they have other nonspecific signs and symptoms. So, this person who's lying in bed and you can see, first of all, the person appears to be quite thin. In fact, weight loss is very common as a nonspecific finding of any chronic illness, but in this context, tuberculosis. Other common so-called systemic symptoms associated with tuberculosis are fevers and the fevers may go on for a long period of time, days to weeks to months. The fevers may be associated with sweating, and that sweating often is most prominent at nighttime, I'm not sure why, but that's so called night sweats, and this combination, of course, makes somebody just feel generally unwell, they have so-called malaise, they don't want to eat, so they're anorexic and that contributes to the weight loss. These are the systemic symptoms that may accompany any kind of tuberculous infection, including lung disease. Then there are some signs, in addition to the signs you will get because you have pneumonia, so the clinical signs associated with pneumonia, or the clinical signs associated with progressive pulmonary symptoms, things like cough, shortness of breath, inability to breathe well, especially when laying down at nighttime. In addition to those findings, there are some other nonspecific things that you should keep in mind when you're contemplating TB as a diagnosis and they're shown in the pictures. One picture, the bottom picture is of the legs of a young individual who has tuberculosis and it shows these elevated, red nodules. Red, erythema, and nodular, nodosum, and this is referred to as erythema nodosum. It is not specific to tuberculosis. It can occur in other diseases, including some fungal infections, like that caused by coccidioidomycosis, and including streptococcal infections, but it also is associated with tuberculosis and the upper picture, of course, is an eye and this is showing a particular form of conjunctivitis, so redness of the eye, and that is referred to as phlyctenular conjunctivitis and that is something which is associated with tuberculosis as well and I wouldn't worry too much about spelling it because it's kind of difficult to spell. Voiceover: All right, well - Voiceover: As Morgan is demonstrating. L-Y-C-T-E-N-U-L-A-R, phlyctenular. Voiceover: Phlyctenular. Voiceover: Conjunctivitis. These are some of the signs and symptoms that may be associated with tuberculosis in general in pulmonary TB, which is the predominant form of clinical disease. Voiceover: Okay. Voiceover: The final thing we'd like to spend a few moments talking about, because it's at least in the chest cavity is pleural tuberculosis. This is little bit distinct from pulmonary tuberculosis, of course the pleural membrane is that which surrounds the lung and pleural disease caused by tuberculosis can result in one of two ways. One is that it may be associated with the first infection, primary infection and it is said that it can be due to hypersensitivity, so an immune reaction of the body to the infection. Then the other way that it can result, either from primary disease, or I think with secondary disease, as well, is as a result of contiguous spread. Direct spread of the infection from the lungs into the pleural space. One of the distinguishing features of pleural tuberculosis, compared to other forms of a pleural infection is that the effusions may really be quite large. The one that you've drawn showing it in the lower part of the left lung, is a modest-sized pleural effusion, but sometimes it can be even larger than that and extend along the whole side of the pleural space. A large pleural effusion, when you see that, you should think of tuberculosis as sort of one cause. Pleural effusions result in an extension of the pulmonary symptoms. You can imagine because they're squeezing down the lungs that the person is short of breath. If you percuss their chest on physical examination, it sounds dull, because there's not air that you're percussing, but rather the solid pleural fluid and when you listen to their chest, they may have decreased breath sounds, because you're not hearing the lung as clearly, because the pleural fluid is in between the stethoscope and the lung. The best way to figure out what's causing a pleural effusion in general and for tuberculosis specifically, is to sample the pleural fluid, to do a pleurocentesis, a pleural tap. When you do that, the typical findings are that the fluid appears straw in color, so yellowish in color, it typically has a very high protein concentration, a low to normal glucose concentration, and white cells that number between 500 and a few thousand. Voiceover: Is that high or low? Voiceover: That's high, there should be no white cells in the pleural space. There should be no pleural fluid, so 500 to a few thousand. With a bacterial effusion, it may be a much higher white count than that, but with TB it's in that range. You can try to visualize the TB in the pleural fluid by doing a TB specific stain, such as a Ziehl-Neelson stain, or a ZN stain. Voiceover: So it's Z-I-E-H-L-N-E-E-L-S-E-N stain and that's actually looking for the tuberculosis bacteria. Voiceover: Right. Voiceover: Okay. Voiceover: The Ziehl-Neelsen stain is positive somewhere between 10 and 25% of the time when TB is actually there, so it's not very sensitive. Culturing the fluid is more sensitive. It takes a longer time, it can take up to four to six weeks to culture and it has a sensitivity in the range of 25 to 75%. Actually, the best sensitivity and the test, therefore, that you should do, if you think that this effusion represents tuberculosis is to biopsy the pleura itself and a pleural biopsy has a yield of about 80%. If you think somebody's got pleural TB with an effusion, pleural biopsy certainly should be done.