ANNOUNCER: The exact cause of psoriatic arthritis is unknown. But the disease tends to run in families and studies point to a genetic link.
BRUCE STROBER, MD: If you have one parent with psoriasis or psoriatic arthritis, your chance of getting the condition is probably somewhere between 10 and 30 percent through your lifetime. If both parents are affected, it's probably between 25 and 60 percent.
ANNOUNCER: Scientists have identified specific genetic makers that predict whether or not a patient is likely to develop the disease.
DAFNA GLADMAN, MD: Certain genetic factors are risk factors for progression of joint damage. So for example, there are certain markers on our lymphocytes that are called HLA antigens.
ANNOUNCER: Environmental factors also appear to be part of the cause.
BRUCE STROBER, MD: This is a genetic condition that requires something in your lifetime to occur, some sort of environmental exposure, maybe an infection and most likely a bacterial infection at some point in your teens or twenties, or maybe a viral infection at those ages. So both your genes and that to which you're exposed during your lifetime will really determine whether you get this condition.
ANNOUNCER: Immunological factors also play a role. A normal immune system protects the body from invaders like bacteria or viruses but psoriatic arthritis patients' systems misfire causing skin cells to reproduce rapidly and joints to become inflamed.
PHILIP MEASE, MD: It's where your immune cells, your white blood cells, misread the cells in your own body and mistake them for something foreign and end up attacking them. And so the cells of the skin, the cells of the joint, the cells of the tissues around the joint, these are attacked by your immune cells.
ANNOUNCER: And the behavior of these cells is influenced by proteins called cytokines.
PHILIP MEASE, MD: These molecular messengers go around and communicate with different cells and tell them, "Hey, come to this place where we want you to get turned on and do inflammation."
BRUCE STROBER, MD: It's clear now that people with arthritis and people with psoriasis rely upon a specific chemical in the body to not only induce the skin problems and the joint problems, but to perpetuate them, to keep them going through life. That chemical is tumor necrosis factor: TNF.
No matter what the causes, early diagnosis and aggressive therapy is important.
BRUCE STROBER, MD: Left untreated, the inflammation in the joint can result in damage that's not reversible and therefore permanent disability in that joint could result.
DAFNA GLADMAN, MD: If a patient comes into the clinic with a large number of affected joints, they're more likely to have disease progression, more likely to develop more severe disease. The other thing that we have found is that more inflammation at the beginning is more predictive of severe disease.
PHILIP MEASE, MD: We have learned that there may be premature mortality in people with psoriatic arthritis. And we think that if we can control the inflammation early, that not only will we prevent disability down the road, but we may even prolong the life of people with psoriatic arthritis.
ANNOUNCER: New therapies are giving patients greater control over the symptoms of their disease and significantly improving quality of their lives.