In our discussion of upper respiratory tract infections,
there’s probably none more important than acute pharyngitis.
So I will speak to you about that.
First, let’s define it.
Acute pharyngitis would be inflammation of the pharynx
from multiple infections and noninfectious causes characterized by this triad:
fever, sore throat, and pharyngeal inflammation.
In terms of the epidemiology, this is a very, very common problem
in the course of a year.
Almost 50% of children will have an episode of pharyngitis
and almost 20% of adults have pharyngitis in the course of one year.
Most of the patients who have it are between the ages of 5 and 24.
And in temperate climates, we find most of the pharyngitis when people
tend to be indoors winter and early spring.
And this is a very unfortunate fact
that when patients go to the doctor with complaints of pharyngitis,
they get antibiotics far too often.
Antibiotics are not necessary in many cases.
So what are the key elements of how these various pathogens cause sore throat?
The exact mechanisms actually
causing the symptoms and signs are not fully understood.
There’s been some evidence that bradykinin, prostaglandins
act on sensory nerve endings,
but that’s not absolutely clear.
The organism that’s been studied most extensively
and we’ll talk most extensively about is group A streptococcus.
But actually, most sore throats are viral
and can be caused by common cold viruses, like the coronavirus,
but also, influenza virus, coxsackie,
or Epstein-Barr virus notorious for causing infectious mononucleosis.
And here I’m showing you a picture of group A streptococcal pharyngitis,
but more about that later.
Let’s talk about the pathogenesis
of pharyngitis caused by group A strep.
This organism is notorious, it has multiple virulence factors,
probably the most important of which is M protein.
It’s also got a hyaluronic capsule.
And the group A strep is able to adhere to epithelial cells of the pharynx
through things that most people refer to as fimbriae.
Some scientists call them pili,
and in these fimbriae are fibronectin-binding proteins and lipoteichoic acid,
and that’s how group A strep adheres primarily to the epithelium.
And once it adheres, it’s able to spread through pharyngeal tissue
through enzymes that can destroy tissue,
like hyaluronidase, streptokinase,
DNAses, and a variety of exotoxins.
So this is really quite a virulent organism.
But back to what I said earlier,
most causes of pharyngitis are viral, 25% to 40% as a minimum,
and these include adenovirus, rhinovirus another common cold virus,
enterovirus, and we can’t forget influenza A and B.
But usually, influenza is a much more serious and troublesome infection.
So they may have pharyngitis, but they’re usually sick in many other ways
and other viruses can cause it.
Of course, group A strep is an important cause because we have treatment for that
and it occurs in about 10% to 15% of adults,
which means that when an adult gets a sore throat,
only about 10% to 15% of the time is it due to group A strep.
On the other hand, when kids get a sore throat,
we’re pushing almost a third of them have group A strep as the cause.
Anaerobes can also cause pharyngitis,
particularly notorious is Fusobacterium necrophorum.
We’ll have more to say about that later.
And then there are some others that physicians must at least consider,
such as Corynebacterium diphtheriae,
but most people are immunized in developing countries against that organism.
And we certainly need to take a good sexual history
because occasionally Neisseria gonorrhoeae can cause pharyngitis.
Mycoplasma pneumoniae can cause it among young adults particularly college age
people who live in dormitory settings or in the military barracks type settings.
And then among older folks, Chlamydophila pneumoniae is a cause of pharyngitis.