Radiology Cases in Pediatric Emergency Medicine
Volume 5, Case 20
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
This is a 2-1/2 year old male who presents to an
acute care clinic with a chief complaint of coughing and
fever. He began coughing three days ago. His cough
is now sounding worse. It sounds harsh and on further
inquiry, it sounds like a barking seal. He was noted to
be warm yesterday, but his temperature was not
His past history is largely negative, but his
immunization status is incomplete. He immigrated from
Asia two weeks ago. He is known to have been
immunized, at least partially, against typhoid and polio.
He had a negative TB skin test at 12 months of age.
He probably has not received any MMR or DPT
Exam: T38.3 (rectal), P100, R24, BP 109/73,
oxygen saturation 95% to 99% in room air. He is alert,
but is noted to be drooling. He has stridor at rest with
mild retractions. An occasional croupy cough is noted.
He does not appear to be toxic. Head normocephalic.
Eyes clear and moist. No pallor. Nose clear mucus.
Oral mucosa pink and moist. Thick yellow and white
exudates are noted on the tonsils, the uvula, and the
posterior pharynx. The epiglottis is not visualized.
Neck supple, with several 1 cm nodes. Heart regular,
no murmurs or gallops. Lungs with inspiratory stridor at
rest. Aeration is good. No wheezes or rales.
Abdomen negative. Normal genitalia. Color, perfusion,
pulses and turgor are good. Strength and movement
good. Sensation intact. He is able to ambulate.
A lateral neck and chest radiographs are obtained.
View lateral neck radiograph.
View chest radiograph.
This lateral neck radiograph shows a normal
epiglottis and no pre-vertebral soft tissue widening.
There is significant subglottic narrowing. While this is
radiographically consistent with croup, this patient
clinically may have more than just croup. The oral
exam in croup is most often normal. The epiglottis can
often be visualized if the patient is cooperative and can
open widely enough. In other instances, the epiglottis
can be visualized by depressing the tongue with a
tongue blade. In this patient's case, his exam reveals
extensive exudates over his tonsils. Additionally,
exudates are noted on the posterior pharynx and uvula.
Because of his lack of DPT immunization, diphtheria
is suspected. He is hospitalized in an intensive care
unit. He is treated with IV penicillin and diphtheria
anti-toxin. A cardiac work-up is negative. During
hospitalization, his stridor worsens and he requires
intubation. During intubation, his larynx and epiglottis
are noted to be edematous. Following intubation, his
condition improves. He is eventually extubated and is
subsequently discharged in good condition. Throat
cultures for diphtheria are positive. Nasopharyngeal
cultures for diphtheria are negative. Group A
streptococcal cultures are negative.
Corynebacterium diphtheriae are gram positive
pleomorphic rods. However, they stain irregularly and
their morphology depends on the media that they are
C. diphtheriae causes clinical disease by infection of
tissues and/or through the elaboration of toxin. The
clinical signs and symptoms of diphtheria depend on
the site of infection, the immunization status of the
patient, and whether or not toxin is being produced by
C. diphtheriae generally infects mucosal surfaces.
While the eyes and genital mucosal surfaces are
occasionally involved, C. diphtheriae, most often infects
nasal, tonsillar, pharyngeal, laryngeal, and tracheal
Nasal diphtheria presents as a mild upper
respiratory infection progressing to serosanguinous and
mucopurulent nasal discharge with nasal excoriation. A
white membrane may be visible on the nasal septum
and a foul odor may be present.
Tonsillar and pharyngeal diphtheria have symptoms
similar to a severe tonsillitis. A white membrane is
visible covering the tissues including the uvula, palate,
tonsils, and pharynx. The membrane may extend down
into the larynx and trachea (visible on laryngoscopy
and/or bronchoscopy). Attempts to remove this
membrane, result in bleeding. Lymphadenopathy
and/or generalized edema of the neck may be evident.
Partially immunized patients may have incomplete
presentations such that the white membrane does not
Laryngeal diphtheria results from downward
extension of pharyngeal diphtheria. Laryngeal
involvement is characterized by croup-like symptoms
such as stridor, drooling, hoarseness and a barking
cough. Airway obstruction is more likely to progress to
a severe degree. The trachea and bronchi may also be
involved. Radiologic features of laryngeal diphtheria
may be identical to viral croup (i.e., mild to moderate
subglottic edema). However, the clinical features,
especially the appearance of the pharynx is usually
different. In severe cases of laryngeal diphtheria, a
membrane may be visible on the lateral neck
radiograph and the degree of subglottic edema seen
radiographically is more severe. This radiographic
appearance is termed, "membranous croup".
View membranous croup radiograph.
This radiograph shows subglottic narrowing. The
black arrow points to a distortion within the airway
resembling a membrane. To appreciate this, you must
turn down the room lights and step back away from the
monitor. Hopefully, you can now appreciate some
distortion in the airway.
The differential of membranous croup is not limited
to diphtheria. It also includes bacterial tracheitis (also
called bacterial croup or bacterial
laryngotracheobronchitis) and anatomic laryngeal
anomalies such as laryngeal/tracheal webs. The
presence of the membrane cannot be relied upon to
make the diagnosis since it is only rarely visible. The
diagnosis of diphtheria, bacterial tracheitis, and
laryngotracheal anomalies must often be made clinically
and later confirmed by CT, fluoroscopy, laryngoscopy
or bronchoscopy. Patients with bacterial tracheitis will
usually appear toxic. They may have high fever and a
leukocytosis. Their airway symptoms are generally
more severe and they may rapidly worsen.
Laryngotracheal anomalies usually have a prolonged or
recurrent course of airway difficulty.
Systemic complications of Diphtheria
Toxin elaborated by C. diphtheriae is cardiotoxic and
neurotoxic. Not all C. diphtheria infections result in
toxin production since toxin production depends upon
the strain of the bacteria and often whether a phage
virus is present. Early administration of antitoxin can
prevent the toxin mediated complications.
Myocarditis may develop during the second week of
illness. Signs and symptoms of myocarditis include
congestive heart failure, tachycardia, muffled heart
tones, murmurs, and dysrhythmia. Myocardial
complications are generally reversible following
antibiotic treatment, anti-toxin administration, and
eradication of the C. diphtheriae infection.
Neurologic complications appear after varying latent
intervals. Examples include paralysis of the soft palate,
oculomotor paresis, dysphagia, diaphragmatic
weakness, peripheral neuropathy, etc. Since these
complications are largely motor and CSF protein is
elevated, these findings are difficult to distinguish from
Rare complications include vascular instability,
gastritis, hepatitis, nephritis and hemolytic uremic
The diagnosis of diphtheria should be made
clinically. Waiting for cultures to confirm the diagnosis
may result in a delay in anti-toxin administration and
toxin-mediated complications. Material from beneath
the white membrane or the membrane itself should be
sent for gram stain and culture. Fluorescent antibody
and other rapid immunologic methods may be able to
confirm the identification of the organism right away. A
"Schick" test may be used to determine diphtheria
susceptibility, however, its interpretation is not simple
and it cannot be read for 3 to 5 days (refer to other
references for more discussion on the Schick test).
Diphtheria toxoid immunization and antitoxin
Diphtheria vaccine is a toxoid which results in
immunity against the C. diphtheriae toxin. Note that
while the vaccine is directed at the toxin and NOT at the
bacteria, a well-immunized individual is protected from
the toxin and the non-toxin mediated complications of
diphtheria. Diphtheria vaccine does not fully immunize
against infection since carrier states and mild infections
are still possible in immunized individuals. However,
vaccine does prevent severe infection.
While most children in the U.S. are fully immunized
against diphtheria, many adults are not routinely
immunized. While tetanus toxoid is commonly
administered in emergency departments for tetanus
wound prophylaxis, there is no routine for diphtheria
vaccine. For this reason, most emergency departments
administer diphtheria-tetanus toxoid (combined dT)
instead of plain tetanus toxoid when tetanus
prophylaxis is indicated. Pregnancy and known
diphtheria toxoid hypersensitivity are indications for
plain tetanus toxoid (without diphtheria toxoid) when
tetanus prophylaxis is indicated.
The patient in this case had probably not received
any DPT vaccines. Being susceptible, he developed a
severe pharyngeal and laryngotracheal diphtheria
infection. Since antitoxin was administered early, he
sustained no toxin mediated complications.
Diphtheria anti-toxin is of horse serum origin,
therefore horse serum hypersensitivity may occur.
Antibiotics (penicillins and erythromycin) shorten the
course of illness by limiting infection. However,
antibiotics may not be effective in preventing
Feigin RD, Strechenberg BW, Strandgaard BH.
Diphtheria. In: Feigin RD, Cherry JD (eds). Textbook
of Pediatric Infectious Diseases, third edition. W.B.
Saunders, Philadelphia, 1992, pp. 1110-1116.
Fleisher GR. Infectious Disease Emergencies. In:
Fleisher GR, Ludwig S (eds). Textbook of Pediatric
Emergencies, third edition. Williams & Wilkins,
Baltimore, 1993, p 621.
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