NBME 20 Legionella pneumophila (NBME Answers)

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Retired NBME 20 Answers

nbme20/Block 2/Question#8 (reveal difficulty score)
Three elderly residents of an assisted living ...
Legionella pneumophila 🔍 / 📺 / 🌳 / 📖
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submitted by ∗usmle11a(102)

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legionella : very common in advanced age, COPD, immunosuppressed patients and " going back from a residence hall" which probably had a contaminated AX system (basically fits every one in the Q)

adeno X : would present with conjunctivitis, throat pain ... flu virus: not everyone got the disease RSV: no children strep pneumo: would target a larger population of healthy people as well.

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bharatpillai why would they say that the only people who didnt get affected by the disease were people on steroids (lupus nephritis and severe asthma) couldnt have been rsv since it causes croup in children. strep pneumo would cause fever and other systemic signs. i went for adenovirus because uworld says most common causes of copd excacerbation are viral infections... +4

brbwhat I went for adeno forr the same reason. I guess the MAIN HINT is that this is not a copd exacerbation. Since people without prexesting copd also had pneumonia, also people with copd exacerbation will have different presenting symptoms, here it was told, that we are told that dx was penumonia. People with copd exacerbation wouldn’t be diagnosed with pneumonia if it was an adenovirus infections. +4

j44n adenovirus doesnt cause pneumonia its just makes the current COPD sx worse +1

j44n the SLE and asthmatic patient were both considered slightly immunosupressed or theyre just more likely to get something (SLE pt= your B cells are too busy making Ig's to kill your kidney, and the asthmatic is on corticosteroids that aopotose your t cells) but they're not COPD patients so the pneumonmia wont be as severe, all in all legionella causes really really bad pneumonia in COPD patients and less severe (pontiac fever) in those with mild immunosupression +5

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submitted by ∗stepwarrior(29)

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I ruled out most of them because of no evidence of person-to-person transmission and only people with pre-existing conditions were affected. The rest would probably also affect children or other attendees or spread to others in the nursing home.

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submitted by allinthistogether(1)

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Legionella is common causes of pneumonia superimposed on chronic obstructive pulmonary disease.

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asapdoc Im pretty sure so is strept pneumoniae +4

usmleuser007 COPD is also exacerbated by Viral infection: Rhinovirus, influenza, parainfluenza; and Bacterial infection: Haemophilus influenzae, Moraxella catarrhalis, Streptococcus. however, the questions gives a hint that it may be legionella = "weekend retreat" which may be associated with this infection +5

loopers From FA 2017 pg 139: Legionnaires’ disease—severe pneumonia (often unilateral and lobar A ), fever, GI and CNS symptoms. Common in smokers and in **chronic lung disease.** +2

kentuckyfan I also believe that the other attendees showed signs of pontiac fever, which is another hint they tried to get at. +3

luke.10 i did it wrong and chose influenza virus since it is most common infection in COPD but the clue in the Question is that the other attendee didnt get sick since in legionella there is no person to person transmission +2

endochondral but in Uworld s. pneumo is one of the most common bacterial exacerbation of COPD legionella wasn't even mentioned. How do we rule out s. pneumo ? +5

nala_ula maybe because in children s.pneumo causes otitis media? +1

smc213 Another hint made in the Q stem is the location being rural Pennsylvania.... Legionnaires disease was first discovered by the outbreak in 1976 at a convention held in Philadelphia, Pennsylvania. Not sure why I know this fact... +10

hpsbwz Biggest hint towards legionella to me was that they all were at a residence hall... i.e. where there'd be air conditioners and such. +6

stresssweat it says that other people developed pneumonia without needing to be hospitalized and that some people were asymptomatic. You would think walking pneumonia - Legionella +

to sum it up: - environmental source (residence hall) - no person to person transmission - SUPERIMPOSED pneumonia, NOT a COPD exacerbation + common bacteria for superimposed - H. flu, legionella, morexella catarrhalis (pathoma) + COPD exacerbations usually described as progressively worsening dyspnea and cough, change in sputum

+1/- lynn(16)

formatting got messed up and now its unreadable - lets try again

legionella because it's an environmental source (residence hall), no person to person transmission, SUPERIMPOSED pneumonia (NOT a COPD exacerbation)

common bacteria for superimposed - H. flu, legionella, morexella catarrhalis (pathoma)

COPD exacerbations usually described as progressively worsening dyspnea and cough, change in sputum; more often viral than bacterial/fungal (UW)

+3/- lynn(16)

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