22-year-old (male) with fever and sore throat

00:02 A 22 year old student presents to the college health clinic with a one week history of fever, sore throat, nausea and fatigue.

00:11 He could hardly get out of bed this morning.

00:14 There are no pets at home.

00:15 He admits to having recent unprotected sex.

00:18 His vital signs include a fever of 38.3 celsius, a heart rate of 72 beats per minute, blood pressure of 118/63 mmHg and a respiratory rate of 15 breaths per minute.

00:31 On physical examination, he has bilateral posterior cervical lymphadenopathy, exudates over the palatine tonsil walls with soft palate petechiae and an erythematous macular rash on his trunk and arms.

00:47 He also has mild hepatosplenomegaly.

00:51 Which of the following is the most likely diagnosis? Answer choice (A) - rubella Answer choice (B) - acute HIV infection Answer choice (C) - toxoplasma infection Answer choice (D) - infectious mononucleosis and answer choice (E) - streptococcal pharyngitis Now take a moment to come to your own conclusion before we go through it together.

01:22 Now let's tackle this question.

01:23 This is a 2-step question.

01:25 First determine the underlying diagnosis and second, determine the microbiology behind the underlying organism.

01:33 Now let's start with step 1.

01:35 let's determine which of the following symptoms we saw in the clinical vignette are generic or specific to the patient's condition? While this patient has generic symptoms such as fever and sore throat and fatigue, but much more specific are bilateral cervical lymphadenopathy, palatine tonsil exudates, soft palate petechiae, erythematous rash on trunks and arms and also hepatosplenomegaly.

02:03 as a whole, these put together, this is more suggestive of a infectious mononucleosis infection.

02:10 Now, we see what is specific and which is general.

02:13 One thing to note here that is also very-high yield is that the question stem did mention that the patient had fatigue.

02:20 Traditionally, in patients that have infectious mononucleosis, they experience SEVERE fatigue.

02:26 So in this case, the clinical vignette said fatigue, so we place it under the condition of a more generic symptoms.

02:33 But if they had mentioned 'severe' fatigue, then that would have been more of a specific symptom for infectious mononucleosis and we could have thought about it in our more specific symptom category.

02:46 Now, now that we've identified which signs and symptoms that are more specific, and we have a underlying diagnosis, let's look at step 2 which is really coming to a firm conclusion regarding which infectious etiology can produce the clinical symptoms that we see? Now this patient has a history of unprotected sex.

03:04 And this of course raises the risk of an HIV infection.

03:08 But this does not generally present with hepatosplenomegaly and instead patients with an acute HIV infection can be either asymptomatic or they can have skin lesions and diarrhea as common symptoms.

03:21 Now given this patient's age being a young, college aged-student and the presentation is very supportive of infectious mononucleosis, the infection here really is due to Epstein-Barr virus as the underlying microbiology of our disease.

03:37 Now Epstein-Barr virus is what commonly causes infectious mononucleosis or also called the "kissing disease".

03:45 Now refer to this image regarding the clinical presentation of infectious mononucleosis, we see there on the left that we have highlighted several clinical components that you can see on a patient.

03:59 There you have pharyngitis where you have inflammation of the pharynx.

04:03 This is where the patient gets sore throat.

04:06 Now this sore throat clinically is VERY severe.

04:09 Some patients with infectious mononucleosis will experience such severe difficulty swallowing that sometimes, they actually have to be hospitalized for IV fluid administration because they can't take oral intake.

04:24 The next thing we see on the image are swollen lymph nodes, or what's also called 'lymphadenopathy'.

04:30 Now what's very specific here is, it was mentioned the patient has 'bilateral posterior cervical lymphadenopathy' Now posterior cervical lymphadenopathy is not specific only to infectious mononucleosis but with respect to the USMLE step 1 exam and step 2 and step 3, posterior cervical lymphadenopathy is essentially a buzz word for infectious mononucleosis.

04:53 Now we also see that you can have splenomegaly, hepatitis or hepatosplenomegaly.

04:58 We see there a virus showing the Epstein-Barr virus.

05:01 And we also see the atypical lymphocyte that are seen with the disease.

05:05 So in this case, the correct answer is answer choice (D) - infectious mononucleosis caused by Epstein-Barr virus.

05:14 Now let's go through some high-yield facts regarding the Epstein-Barr virus and infectious mononucleosis.

05:20 Now Epstein-Barr virus is a type of human herpesvirus that is found in the saliva and in the genital secretions and it causes what is called infectious mononucleosis or what was previously called glandular fever.

05:35 Now as we know, Epstein-Barr virus is actually associated with a certain malignancy called Burkitt's lymphoma - that's very high-yield to know.

05:45 Now infectious mononucleosis also called previously glandular fever is caused by Epstein-Barr virus.

05:51 Now you will most commonly see this infection in teenagers and in young adults.

05:57 And oftentimes, people obtain this disease and are asymptomatic.

06:01 However, in some instances, people become very symptomatic in which they will have a high fever, an extremely sore throat that can limit oral intake, erythematous spots on the mouth or petechiae, bilateral posterior cervicolymphadenopathy, and hepatosplenomegaly and they will have VERY significant fatigue in some instances