Hardcore Psoriasis Intro

[Moxtina]

As far as I know, and what I have seen and read in practice, Psoriasis is defined as touching the skin, while psoriatic arthritis is touching joints (mostly the small ones) and has a tendency to also touch the tendons.
Not more, at least then it is not called Psoriasis anymore.

Well, yes and no. Psoriasis is finally becoming known as a *systemic immune-mediated disease that is kind of assumed to affect multiple organ systems. A bit like Lupus. In fact, many of us who have Psoriatic Disease actually have similar antibodies and it can be difficult to distinguish between the two if certain signs aren't present - like the "butterfly rash" in lupus or characteristic scaling of plaque or guttate psoriasis.
So much depends on what kind of specialist you're seeing and whether or not THEY are aware of the latest discoveries, etc. Or if they encourage you to be educated on the disease and welcome your research and commentary. I finally found a rheumatologist who IS and he's amazing and he respects me and my research, often engaging me in conversations about it and backing up my theories, answering questions and running  tests that no other rheumy would do previously. 
I guess what I'm saying is that it's been pretty well established that there are co-factors, co-morbidities and correlations between Psoriatic Disease and the inflammation of other organ systems, especially the gut, eyes, heart, liver, kidneys, pancreas, etc. People with Ps/PsA are also notably afflicted by diabetes, high blood pressure, Crohn's disease, metabolic syndrome/obesity, and lipid anomalies. 
Research has established a link between psoriasis and cardiovascular complications, which is highest in patients with severe and relatively early onset psoriasis. Even when smoking, obesity, and stress are factored in and accounted for, there is a markedly higher risk factor than for those who do not have this disease.
Basically, inflammation is the thread which connects psoriasis to all the other afflictions. A great deal of it is heavily dependent on your genetic makeup.
And your genetic makeup, in part determines your response to different medications and treatments. For instance, those with a certain gene sequence will not respond to TNF inhibitors but WILL respond to IL-23 inhibitors. Those with another gene sequence will actually get very ill if they take methotrexate or plaquenil.
It's pretty fascinating... and overwhelming!