54-year-old (Male) with Shortness of Breath

00:01 Okay, guys we got a fascinating question here.

00:04 A 54-year-old man presents to the office complaining of a recent shortness of breath and fever.

00:12 He has a history of chronic cough which is progressively getting worse.

00:19 His medical history is significant for hypertension and diabetes mellitus, both controlled with medications.

00:28 He has been working in a sandblasting factory for over three decades.

00:35 His temperature 37.7 degrees Celsius.

00:39 The blood pressure is a 130/84.

00:43 The pulse is 98 and respirations are 20.

00:47 The chest x-ray reveals calcified hilar lymph nodes which look like an eggshell.

00:55 This patient is at increased risk for which of the following conditions? Answer choice A: Chronic obstructive pulmonary disease; Answer choice B: Adenocarcinoma of the lung; Answer choice C: Mesothelioma; Answer choice D: Pulmonary embolism; or Answer choice E: Mycobacterium tuberculosis infection Now, take a moment to come to the answer yourself before we go through it together.

01:29 Okay, now this is a really important question because it's subtle but there is some really high-yield, often tested material in here.

01:39 So, let's look at the question characteristics.

01:42 Well, this is an internal medicine question and we have a guy with cough with respiratory complains so this is a respiratory question.

01:51 Now, this is a two-step question.

01:53 The first thing we have to do is figure out the diagnosis of what this person has and then second, we have to figure out what condition are they at an increased risk of, given the diagnosis.

02:07 And here, of course, the stem is absolutely required because you need to be able to filter through various components of the information in the question stem to come to the right answer.

02:19 So let's walk through the question, first trying to determine the diagnosis.

02:24 Now, we have a male patient who has come to us with the chief complaint of shortness of breath.

02:31 Now, shortness of breath really gives you a wide differential diagnosis and really is a very common condition when patients present to the emergency room.

02:42 Respiratory causes can cause shortness of breath including asthma, COPD, pneumonia, pulmonary embolism, etc, but this patient can also have cardiac causes that would give you shortness of breath.

02:59 That could be congestive heart failure with pulmonary edema, it could be an arrhythmia with pulmonary edema, etc.

03:06 So differential really here is both wide for cardiac and respiratory.

03:11 For the associated symptom, the patient tells you that they have a fever, which is a recent onset, and chronic cough.

03:21 Now, these are both progressively getting worse and that the chronic cough has been getting worse for the patient.

03:28 Now the chronic cough, though, is really suggestive of an underlying respiratory disorder and that really helps us out.

03:38 But, there is a subtle point I want you to keep in the back of your mind when taking USMLE, is that chronic cough can also be caused by ACE inhibitors or angiotensin-converting-enzyme inhibitor, which are medications to, of course, treat blood pressure.

03:55 Now we're -- we know that is patient has elevated blood pressure and is taking medications but we're not told what these medications are.

04:05 So in the back of your mind, you have to keep in there to say, "Well, could it be an ACE inhibitor giving you this chronic cough?" But the fact that it's getting progressively worse makes an ACE inhibitor as the causeless likely but I bring it up because that's where I want your brain to go.

04:23 That's where mine goes, maybe that's where yours should go because that kind of thinking puts you on a guard for the tricks of USMLE.

04:31 Now the occupational history for this patient is outrageously significant.

04:38 He has been spending three decades in a sandblasting factory which tells us that he has prolonged exposure to dust particles.

04:48 Now we also need to use the x-ray results in the question and that the patient has eggshell calcifications.

04:56 Now that alone, given the fact that they've been working in a sandblasted factory, and having respiratory complains, is really characteristic of a condition called silicosis, which is an occupational lung disease caused by the inhalation of silica dust.

05:18 Thus, the diagnosis for this patient is silicosis.

05:22 Now, what we next have to figure out is what condition is associated with silicosis.

05:29 Now, in silicosis, you have inflammation and scarring of the lung tissue.

05:37 These are actually called nodular lesions and what it actually produces is a restrictive lung disease.

05:45 Now, malignancy is not commonly associated with silicosis but it can actually be associated with other inhalation syndromes.

05:57 Such as adenocarcinoma of the lung can be associated with smoking tobacco, or mesothelioma could be associated with inhalation of asbestos.

06:09 Thus, we can then know that the most likely cause for this patient is answer choice E, which is Mycobacterium tuberculosis infection because the other answer choices can be readily eliminated.

06:24 Let's go through them quickly now, and then again in detail.

06:27 Answer choice A: COPD, wrong.

06:29 Silicosis produces a restrictive lung disease, not obstructive.

06:35 Adenocarcinoma of the lung, no.

06:38 That patient would need to be smoking tobacco, not silica dust. Mesothelioma, answer choice C, wrong.

06:45 That patient would have to be inhaling asbestos, not silica dust.

06:50 Answer choice D: pulmonary embolism, wrong.

06:54 Silicosis has nothing to do with the vasculature, it only affects a lung parenchyma, doesn't increase your risk of clotting, not related.

07:03 So you can eliminate answer choice A through D and come to the conclusion that it an affection of Mycobacterium tuberculosis is the most likely consequence of having silicosis, so this is another example of how USMLE can test you -- not be just simply knowing the right answer, but by being able to eliminate the other answer choices as wrong, and then reinforcing with yourself that the answer leftover is the correct answer.

07:35 Now, this patient has silicosis, which is an occupational pneumoconiosis from inhaling the silica dust and this long-term exposure to the silica dust can be found in patients that work in sandblasting, stonework, mining, or volcanic ash. That's really important for you to memorize.

07:58 For you to be given a clinical situation in which you're supposed to think of the diagnosis of silicosis, you have to usually be given some type of occupational exposure, as we just mentioned to even get your brain thinking silicosis.

08:14 Otherwise, it wouldn't make sense. Now if they didn't give you the occupation, but on chest x-ray, you see the classic eggshell calcification pattern of the hilar lymph nodes.

08:26 That's really suggestive of silicosis but it is not pathognomonic.

08:32 Don't rest all your eggs in that basket.

08:35 But in most cases, having that eggshell imaging on x-ray and the story of occupational exposure is enough, as in this case, to come to the diagnosis of silicosis and you don't need to do a tissue biopsy.

08:51 Now, it's important for you to know that patients with silicosis are actually susceptible tuberculosis infections.

09:00 Now, the exact mechanism here is unknown but it's theorized that the silica dust damages the macrophages and that results in a decreased ability to recognize and destroy infectious antigens like mycobacterium.

09:18 That's how answer choice E is correct by knowing that silicosis increases your risk of Mycobacterium tuberculosis infection or by being able to eliminate all the other answer choices.

09:32 Again, as we were able to eliminate the answer choices, answer choice A: chronic obstructive pulmonary disease is wrong as silicosis causes a restrictive pulmonary disease, not obstructive.

09:47 Answer choice B being wrong, as adenocarcinoma can be seen commonly in non-smoking females or in smokers exposed to tobacco.

09:59 Or answer choice C, which is mesothelioma which occurs from inhalation of asbestos, not silica.

10:07 And answer choice D being wrong, as silicosis has no vascular implication and there is no increased risk for pulmonary embolism.

10:16 Okay, let's talk about some really high-yield facts for this question stem.

10:21 First thing to talk about is silicosis.

10:24 Now, this is an occupational lung disease and you are going to see it, at least on boards and people who have prolonged exposure to crystalline silica dust, and the buzz word, I want you to search for when doing your boards question is someone who worked in a sandblasting factory.

10:44 That's going to be a buzz word.

10:45 A worker that worked in a sandblaster factory now has respiratory complaints.

10:50 Now the reason why we care about this condition and why silica dust is even important is that it causes inflammation and scarring of the lungs.

10:58 Now what ends up happening is that the lungs cannot remove silica dust from the alveoli.

11:05 So, an inflammatory and scarring reaction occurs.

11:08 Now, if you imagine, the lungs are involved in taking oxygen and throwing it on to the hemoglobin of the blood.

11:14 If you have inflammation and scarring, you've just created more dead space and your lung is less effective.

11:20 Now the symptom onset is gradual and this is key for you to nail the board question.

11:26 The first symptoms are going to appear years after the exposure has stopped and the disease can even progress even after exposure is eliminated.

11:38 So that's a key thing I want you to pay attention to.

11:41 They may mention in the question stem that the patient was a sandblaster but temporally it has to make sense.

11:47 The disease symptom has to happen years later not right away.

11:52 Now how do you diagnose this condition? Well, it kind of works out on your favor.

11:57 The diagnosis is really based on patient history, you know someone working as a silica dust factory, or sandblasting person, and then you can get x-ray imaging and exclude other common causes of other lung diseases.

12:10 Now an important thing here for boards, biopsy is not required.

12:16 So you may see that and you very likely will see that on your boards as an option choice for this question, don't pick it.

12:23 You don't need to get invasive in picking someone up with silicosis.

12:27 Get a history, do imaging, do the diagnosis. How do you treat someone with silicosis? The answer is not -- we don't get that much to offer them.

12:35 Unfortunately, the treatment is symptomatic.

12:38 That means silicosis, unfortunately, causes irreversible damage to the lung tissue.

12:45 We mentioned the inflammation and scarring.

12:47 And apart from getting a full lung treatment, and actually getting a full lung transplant as the treatment, there really isn't much to do and that's quite unfortunate.

12:56 I want you to kinda get that in your head.

12:58 Dust particles flying around, someone who sandblasting, years later they start to get respiratory complains, if you were to look in their lungs, they're going to get inflammation and scarring, lungs don't work that well, and the only way to fix it, if something's all scarred up and damaged, cut it out and throw in a new pair of transplanted lungs.

13:17 Another really high-yield topic that you will see on the board is tuberculosis.

13:22 Now tuberculosis is caused by the infection Mycobacterium tuberculosis.

13:27 Now of course tuberculosis most commonly affects the lungs but don't forget, it affects another of -- other things as well.

13:36 So, outside of the lung, you can have extrapulmonary areas.

13:41 Such as the pleura of the lungs, the central nervous system, the lymphatic system, even bone.

13:48 Think of pox disease can actually have spreading of tuberculosis.

13:53 Now what I want you to think about here is if you have someone who is coming in and you think they have extrapulmonary manifestations of tuberculosis, this is likely an immunodeficient or an immunosuppressed individual, so keep that on your radar.

14:06 Now tuberculosis is transmitted through aerosol droplets and if you imagine, when you see TB patients on the ward, you're gonna wear an n95 mask because you want to protect yourself from the droplets.

14:19 Now, there are various risk factors for tuberculosis such as being an endemic area or having a poor immune system, but also chronic lung disease such as silicosis increases your risk of getting tuberculosis.

14:33 Now the pathophysiology interestingly of silicosis associated tuberculosis is poorly understood but it's thought to be related to deficient macrophages and of course, treatment for tuberculosis is antibiotics with right therapy and it's the same treatment even if you have silicosis associated tuberculosis.