John R. Tkach, M.D.
300 North Willson, Suite 203B
Bozeman, MT 59715
(406) 587-5442


Patient Information Sheet

Psoriasis is an inherited disease that causes areas of thick, red scaly skin called "plaques". It is inherited in a complex manner called polygenic. It seems to involve an interaction between several different genes on different chromosomes. The cause is still unknown.

It is possible to inherit the genes for psoriasis but never actually get psoriasis. Usually, there is a family history of psoriasis, but sometimes it will seem to skip generations. That is you can inherit psoriasis, but never break out. And then your children may express psoriasis.

The expression of psoriasis is extremely variable. Most people don't have a whole lot of trouble with psoriasis. Some people with psoriasis only get a few small spots of psoriasis in their whole lives. Sometimes it will affect only certain areas such as the elbows or knees or fingernails or scalp. A few people get psoriasis from head to toe and have a lot of difficulty with it.

Psoriasis is not an infection. You cannot give it to other people by touching them. You did not get it by touching someone else. It is okay to swim in public pools without endangering your friends. If people ask you about it, just tell them that it is psoriasis. It is not contagious, and you are having it treated by a doctor.

We do not know the cause of psoriasis and do not have a cure. What I can do is to help you control it. Generally, we can clear it up, but it will tend to come back. Most of the time, psoriasis is fairly easy to treat, but sometimes it is very hard to treat.

Rapid Growth of Skin Cells

The standard theory of the cause of psoriasis is that it is due a genetic defect that causes the skin to grow too fast. There is no doubt that the skin cells are growing faster than normal in psoriasis, but I think inflammation component may be more important.

To understand psoriasis better, let's take a look at the normal skin (those areas that don't have an outbreak of psoriasis). There is an outer living layer of skin called the EPIDERMIS. The bottom layer of the epidermis is the BASAL layer. This is where theskin cells start growing from. A basal cell divides into two cells. After a basal cell divides, one daughter cell moves upward, and the other remains in the basal cell layer to divide again in the near future.

The cells moving outward comprise most of the epidermis. As they reach the outside, they change and form a protective outer layer of dead skin. Eventually this layer is shed. It takes about a month for the cells to make this journey. And the process is going on slowly all the time. Below the epidermis is a layer containing the dermis. The dermis contains the blood vessels that supply oxygen and nutrition to the epidermis. It also contains the nerves that supply feeling to the skin.

In the areas of psoriasis, the skin is growing 12 times faster than normal.

Normal Skin

Normal Skin

Skin with Psoriasis


The normal basal cell will divide about once every 457 hours. In psoriasis, the basal cell divides about once every 37.5 hours. This means that in the areas of psoriasis, the skin is growing about 12 times faster than normal. It is growing so fast that the cells pile up on top of each other making the skin thicker. The dead skin layer forms so fast it does not have time to be shed. So, there may be a thick layer of scale. Small air bubbles get trapped inside the thick layer of dead skin giving it a silvery color.

In order to supply enough food for the rapid rate of growth of the skin, the blood vessels dilate making the psoriatic plaque red. Blood vessels grow upward extending unusually close to the surface of the skin. The blood vessels are so close to the surface that picking away the scale causes a plaque to bleed a little. Inflammation causes the plaques to become itchy.

The Koebnerization Phenomenon

Minor injuries such a cuts, scrapes, and burns will often heal leaving a plaque of psoriasis. This induction of psoriasis by injury is called Koebnerization. The skin of the elbows gets pinched hundreds of times a day when we lean on hard surfaces such table tops and arm rests of chairs. This tiny injury produced many times a day causes the elbows to be a common site of psoriasis.

Some infections, most notably beta streptococcus, as in strep throat, can lead to the formation of hundreds of tiny plaques all over the body. We think the bacteria actually get into the skin and damage it thus inducing the small plaques. This phenomenon is called GUTTATE PSORIASIS. If you get this, it means that you need an antibiotic such as penicillin. Sometimes, if recurrent episodes of guttate psoriasis are due to Strep throat, a tonsillectomy can help.

Psoriatic Arthritis

n my opinion there is about a 7% risk of developing psoriasis in the joints. Manufacturers of expensive anti-arthritis drugs claim that it is between 25% and 49%. Psoriasis developing in a joint lining produces a peculiar form of joint disease called psoriatic arthritis. It greatly resembles rheumatoid arthritis but tends to be less severe. The RA factor lab test is negative. The CCP test can be positive, but that does not distinguish between the two. This diagnosis is by clinical impression and not by lab studies.

Avoiding Systemic Cortisone

The use of systemic steroids such as cortisone, prednisone, Kenalog, Decadron, Medrol and so on will temporarily improve psoriasis. The problem is that sometimes, when they wear off, the psoriasis may come back many times worse. If possible, avoid using cortisone pills and deep muscular injections of cortisone for minor problems. If you have a serious problem requiring cortisone treatment, go ahead and have your doctor give it to you. I'll try to get you through the aftermath. When I say a serious problem, I am thinking of heart attack or overwhelming infection. Sometimes, I treat individual psoriatic plaques with injections of dilute Kenalog just localized to the skin plaques. I take the standard Kenalog and dilute it down about 20 times. In this case, I am using a very small amount of cortisone. This is usually a very effective treatment for very stubborn plaques. The problem is that I can only treat small areas at a time in this way.

Increased Risk of Cancers

In the past, dermatologists thought psoriasis patients had a reduced risk of getting cancer. Beginning around 2008, new studies appeared that concluded that people with psoriasis have an increased risk of internal cancers. Combining 3 studies in the UK, Denmark, and Sweden totalling 59,488 patients, there was an increased risk of 50% to three fold of tumors of the skin, oropharynx, stomach, esophagus, liver, pancreas, lung, kidney, colon, nervous system, leukemia, and lymphoma. This is especially associated with alcohol, smoking, and obesity.


Topical Treatments

The most effective treatment for psoriasis involves the use of topical cortisone creams and ointments. These medicines do several things. They decrease inflammation and itching. They slow down the rapid rate of cell division. They constrict the blood vessels so not as much blood can reach the rapidly dividing cells.

The thick outer layer of dead skin, the scale, of the plaque is a barrier that prevents the medicine from penetrating to where it can go to work. A great way to get around this problem is to wet the skin with a little water before rubbing in the medicine. Studies have shown that the water acts as a vehicle that carries the medicine in 10 times better. If you will take the time to wet the skin before rubbing in the medicine, you will get more for your time and money. Water is much cheaper than cortisone creams.

Sunlight is beneficial for psoriasis, especially a suntan. Avoid getting a sunburn. Watch for getting skin cancer.

In my experience, the cortisone medicine usually clears up the plaques. Sometimes a plaque won't quite go away. When the topical cortisone is stopped, the plaques pop right back. I have found it helpful to use tar in this situation. Use the topical cortisone until the plaque is a flat discolored area. Then switch to tar. Sometimes I will combine the tar with the cortisone cream. Tar shampoos are especially helpful for scalp psoriasis. You can push the tar shampoo a little harder by applying the tar shampoo in the shower, putting on a shower cap or bathing hat, doing something else for an hour, and then washing off the tar shampoo.


Methotrexate has been around since 1948. It has been used for psoriasis since around 1970. Rheumatologists routinely use it for rheumatoid arthritis and for psoriatic arthritis. I started prescribing it in 1973. It is an anticancer drug that slows down cell division, which is too fast in psoriasis. It is a folic acid antagonist the implication being it can cause anemia. In 2012, the future of manufacturing methotrexate became uncertain as producers withdrew from the market.

Methotrexate is very effective. It is taken as a single dose once a week. Sometimes using it for just 6 weeks is enough to get psoriasis under control. I have one patient who has used it continuously since 1982 except for a three-year break.

The problem with Methotrexate is that it can damage the liver and bone marrow. It can make it harder for your immune system to fight infection. If you take Methotrexate, you must not drink alcohol at all. Avoid ibuprofen and grapefruit. It can make you sensitive to the sun. We need to get occasional liver and blood lab studies done. You should not take it if you have liver disease like hepatitis.

Methotrexate will cause severe birth defects if taken a pregnant woman.

Having said all those things, in actual practice, I have had only one person since 1972 who had a serious problem with Methotrexate. Unknown to me he took a very large dose of Ibuprofen, 12 pills, the same day he took his weekly Methotrexate dose. His liver enzymes went up 4 fold. He did recover, and his severe psoriasis went away.

Fusion Proteins/Biologicals

These are new drugs developed for rheumatoid arthritis, and their use has spilled over into psoriasis because they treat psoriatic arthritis. They are all given by injection. They are not pills to be taken by mouth. They cost about $1,200 a month, but there are special arrangements that can reduce your out of pocket cost dramatically. I have two patients on Enbrel and one on Humira all doing very well.

These are drugs that are very large proteins produced by sophisticated molecular genetics engineering. Each one combines an antibody in some form with a chemical the binds to and inhibits Tumor Necrosis Factor. They reduce inflammation is a more specific way than cortisone does. They are big antibodies that block TNF.

The potential problems are the risk of getting a lymphoma and a small but definite risk of a brain disease called Progressive Multifocal Leukoencephalopathy. Enbrel and Humira may be considerably safer than Remicaide.

Dr. Tkach's Theory of Psoriasis

My theory of psoriasis is that psoriasis involves an inherited defect in the regulation of function of the epidermal Langerhans cells. Epidermal Langerhans cells are cells in the epidermis that initiate inflammation. I suspect that in psoriasis the epidermal Langerhans cells are sort of twitchy. They get turned on too easily, turned on when they should not be. Thus they inappropriately trigger inflammation, and all the other aspects of psoriasis are secondary to this defect.

This idea came to me in 1984. The advantages of this theory are that it explains many of the previously puzzling aspects of psoriasis and it proposes a way to look for better treatments. It explains why Koebnerization occurs, why topical steroids, tar, and UV light work, and why tar-UV light treatment gives longer lasting improvement than topical steroids.

Learn more at the National Psoriasis Foundation web site.

The information provided in these patient information sheets is offered for general informational and educational purposes only; it is not offered as and does not constitute medical advice. In no way are any of the materials presented meant to be a substitute for professional medical care or attention by a qualified practitioner, nor should they be construed as such.

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