You are on your pediatric rotation and are asked to examine a 10-year-old girl
with Down's syndrome who was admitted with a 10-day history of fever, rigors, and
progressive dyspnea that had failed to respond to a 5-day course of intravenous gentamicin.
On your exam her BP is 105/70, pulse 110 and regular, temperature 38.5°C, and
respirations 20 breaths/minute. Her breath is fetid. You note a flat percussion note,
absent tactile fremitus, and diminished breath sounds over the right posterior chest.
Her admitting chest x-ray is shown below.
DIAGNOSIS: Bacteroides fragilis aspiraion pneumonia with resultant lung abscess and empyema.
Individuals with Down syndrome (DS) are are at high risk for dysphagia-related
aspiration due to low muscle muscle tone of their esophagus. In turn, aspiration pneumonias
typically involve one or more of the oropharyngeal flora where anaerobes (bacteroides,
peptostreptococci, and fusobacterium) out number aerobic bacteria. Thus, the presented
case had typical consequences of aspiration - Bacteriodes fragilis pneumonia, lung abscess, and empyema. B. fragilis is resistant to aminoglycosides, thus explaining the lack of response of the presnted
case to gentamicin.
Persons with DS are also at increased risk of viral and aerobic bacterial pneumonia
as compared to the general population. Chromosome 21, which is triplicated in DS,
harbors a number of immune-related genes including those that code for interferon
(IFN) receptors, ubiquitin associated and SH3 domain containing A (UBASH3A), and autoimmune
regulator (AIRE). As a result DS patients have reduced chemotaxis, increased IFN responses,
altered TLR signaling, impaired Fcγ and complement responses, reduced responses to
vaccines, and accelerated immune system aging1. Unfortunately, the presented case aspirated the contents of a large right lung abscess
into the left lung (see below) and expired.
Bacteroides fragilis bacterial pneumonia and empyema (left image). Aspiration of the contents of a large right-sided abscess into the left lung (right image).
1. Illouz T., Biragyn A., Iulita M.F., et. al. Immune dysregulation and the increased risk of complications and mortality following respiratory tract infections in adults with Down syndrome. Front. Immunol. 12:621440. doi: 10.3389/fimmu.2021.621440.
BONUS QUESTION ANSWER: a positive Kussmaul sign (lack of collapse of the external jugular vein during inspiration) most commonly due to right-sided congestive heart failure.