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 somewhat 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 tiny 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 scattered 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 the soles of the feet. Of course, these are, again, itchy and tender. These pimples are sterile. There are no bacteria in it, so it’s not a real pimple. It’s just inflammation, but it looks like that. We see this in people with psoriatic arthritis as well. Then, of course, there are more severe systemic forms where most of the skin, 80% to 90% of the surface is affected by a 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 pin and, again, that can have different degrees of severity, from just a few holes 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 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 recover fully. But it’s reversible with effective treatment. (gentle music).