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- 30 to 40 years is the peak age
where people develop psoriatic arthritis,
which is about a decade later
than the peak age for psoriasis, for the skin disease.
People usually take 10 to 20 years
to develop psoriatic arthritis.
In terms of the disease course, it's rather unpredictable.
People will experience episodes of worsening
of the psoriatic arthritis and then episodes of improvement.
Early symptoms with psoriatic arthritis are important.
For example, in the Toronto cohort,
it was shown that people who developed psoriatic arthritis
the year before they were diagnosed
had reported joint pain, fatigue, and stiffness.
So, again, the symptoms,
although they may seem non-specific, are very important
and maybe the initial steps that patients experience
even before they are diagnosed.
Psoriasis is a relatively common skin disease.
It affects about 4% of Americans.
And the form that is most associated
with psoriatic arthritis is psoriasis
that's located on the scalp.
Having psoriasis behind the ear
or inside the ear also counts.
Perianal psoriasis.
And then of course there's the more frequent form
where classic psoriasis is localized on the knees
and on the elbows.
It's very bothersome for patients,
and there's degrees of this.
And then the most classic form is
what we call plaque psoriasis
where people will develop
these raised lesions.
There's a rash that's called guttate psoriasis,
which looks like little drops of rain.
That's how it got its name.
It's just very little patches of rash,
but it's spread over almost the entire body,
so if you add these patches together,
it's a lot.
It's just that they are spread all over.
People tend to get this more often
after strep throat.
It's most common in young people.
That's one form, in addition
to the classic plaque psoriasis.
There's one that's called inverse psoriasis,
where people tend to develop the rash in the skin folds.
It tends to look different
just because the skin in those areas
has a different quality.
It's not going to scale as much,
but it's going to be red,
and it's going to hurt,
and it's going to ooze fluid,
and it's very uncomfortable.
Then there are more rare forms.
About two to four percent of people with psoriasis
will have a rash that's called pustular psoriasis.
It looks like little pimples on the hands
or on the soles of the feet.
Of course, these are, again, itchy and tender.
These pimples are sterile.
There's no bacteria in it,
so it's not a real pimple.
It's just an inflammation,
but it looks like that.
We see this in people with psoriatic arthritis as well.
Then, of course, there's more severe systemic forms
where most of the skin,
80% to 90% of the skin is affected with red rash.
We call that erythroderma.
When that is severe, that sometimes needs hospitalization
and treatment with health and drugs
to try and get the skin under control.
Because if you think the skin is our largest organ,
and it's essential for the body to function properly
and to be protected from everything else around you.
Nail psoriasis can look in many different ways.
The most common form is what we call nail pitting.
There are small pits on the surface of the nail
and, again, that can have different degrees of severity,
from just a few pits on several nails
to really, all the entire nail surface
being changed by that.
Then, the extreme form of pitting would be
nail plate crumbling,
where the nail can turn into a powder
and then it's basically just disintegrating.
Another form is what we call onycholysis,
when the nail lifts off the nail bed.
The nails grow slowly,
so even with treatment,
it takes months for the nail to fully recover.
But it's definitely reversible with effective treatment.
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