- Psoriasis is a chronic, inflammatory skin disease.
- Psoriasis is related to inherited genes and the immune system.
- Plaque psoriasis is the most common form of psoriasis.
- Obesity, diabetes, and heart disease are more common in people with psoriasis.
- Flare-ups of psoriasis can be initiated by certain environmental triggers.
- Although symptoms and signs vary, they include red, scaling plaques of itchy, elevated skin affecting the elbows, knees and scalp.
- Psoriasis is not contagious.
- Psoriasis gets better and worse spontaneously and can have periodic remissions (clear skin).
- Psoriasis is controllable with medication.
- Psoriasis is not curable.
- There are many promising new therapies, including newer biologic drugs.
What is psoriasis?
Psoriasis is a noncontagious, chronic skin disease that produces plaques of thickened, scaly skin. The dry flakes of silvery-white skin scales result from the excessively rapid proliferation of skin cells. Psoriasis is fundamentally an immune system problem. The proliferation of skin cells is triggered by inflammatory chemicals produced by specialized white blood cells called T-cells. Psoriasis commonly affects the skin of the elbows, knees, and scalp.
The spectrum of this autoimmune disease ranges from mild with limited involvement of small areas of skin to severe psoriasis with large, thick plaques to red inflamed skin affecting the entire body surface.
Psoriasis is considered an incurable, long-term (chronic) inflammatory skin condition. It has a variable course, periodically improving and worsening. It is not unusual for psoriasis to spontaneously clear for years and stay in remission. Many people note a worsening of their symptoms in the colder winter months.
Psoriasis, an immune-mediated inflammatory disease, affects all races and both sexes. Although psoriasis can be seen in people of any age, from babies to seniors, most commonly patients are first diagnosed in their early adult years. The self-esteem and quality of life of patients with psoriasis is often diminished because of the appearance of their skin. Recently, it has become clear that people with psoriasis are more likely to have diabetes, high blood lipids, cardiovascular disease, and a variety of other inflammatory diseases. This may reflect an inability to control inflammation. Caring for psoriasis takes medical teamwork.
Picture of plaque psoriasis on the legs. Source: iStock.com.
Quick GuidePsoriasis Types, Images, Treatments
Is Psoriasis Contagious?
No. Psoriasis is not contagious. Psoriasis is not transmitted sexually or by physical contact. Psoriasis is not caused by lifestyle, diet, or bad hygiene.
While the exact cause of psoriasis is unknown, researchers consider environmental, genetic, and immune system factors as playing roles in the establishment of the disease.
What are psoriasis causes and risk factors?
The exact cause remains unknown. A combination of elements, including genetic predisposition and environmental factors, are involved. It is common for psoriasis to be found in members of the same family. Defects in the immune system and the control of inflammation are thought to play major roles. Certain medications like beta-blockers have been linked to psoriasis. Despite research over the past 30 years, the "master switch" that turns on psoriasis is still a mystery.
What are the different types of psoriasis?
There are several different forms of psoriasis, including plaque psoriasis or psoriasis vulgaris (common type), guttate psoriasis (small, drop-like spots), inverse psoriasis (in the folds like of the underarms, navel, groin, and buttocks), and pustular psoriasis (small pus-filled yellowish blisters). When the palms and the soles are involved, this is known as palmoplantar psoriasis. In erythrodermic psoriasis, the entire skin surface is involved with the disease. Patients with this form of psoriasis often feel cold and may develop congestive heart failure if they have a preexisting heart problem. Nail psoriasis produces yellow pitted nails that can be confused with nail fungus. Scalp psoriasis can be severe enough to produce localized hair loss, plenty of dandruff, and severe itching.
Can psoriasis affect my joints?
Yes, psoriasis is associated with inflamed joints in about one-third of those affected. In fact, sometimes joint pains may be the only sign of the disorder, with completely clear skin. The joint disease associated with psoriasis is referred to as psoriatic arthritis. Patients may have inflammation of any joints (arthritis), although the joints of the hands, knees, and ankles tend to be most commonly affected. Psoriatic arthritis is an inflammatory, destructive form of arthritis and needs to be treated with medications in order to stop the disease progression.
The average age for onset of psoriatic arthritis is 30-40 years of age. Usually, the skin symptoms and signs precede the onset of the arthritis.
Can psoriasis affect only my nails?
Yes, psoriasis may involve solely the nails in a limited number of patients. Usually, the nail signs accompany the skin and arthritis symptoms and signs. Nail psoriasis is typically very difficult to treat. Treatment options are somewhat limited and include potent topical steroids applied at the nail-base cuticle, injection of steroids at the nail-base cuticle, and oral or systemic medications as described below for the treatment of psoriasis.
What are psoriasis symptoms and signs? What does psoriasis look like?
Plaque psoriasis signs and symptoms appear as red or pink small scaly bumps that merge into plaques of raised skin. Plaque psoriasis classically affects skin over the elbows, knees, and scalp and is often itchy. Although any area may be involved, plaque psoriasis tends to be more common at sites of friction, scratching, or abrasion. Sometimes pulling off one of these small dry white flakes of skin causes a tiny blood spot on the skin. This is a special diagnostic sign in psoriasis called the Auspitz sign.
Fingernails and toenails often exhibit small pits (pinpoint depressions) and/or larger yellowish-brown separations of the nail from the nail bed at the fingertip called distal onycholysis. Nail psoriasis may be confused with and incorrectly diagnosed as a fungal nail infection.
Guttate psoriasis symptoms and signs include bumps or small plaques (½ inch or less) of red itchy, scaling skin that may appear explosively, affecting large parts of the skin surface simultaneously, after a sore throat.
In inverse psoriasis, genital lesions, especially in the groin and on the head of the penis, are common. Psoriasis in moist areas like the navel or the area between the buttocks (intergluteal folds) may look like flat red plaques without much scaling. This may be confused with other skin conditions like fungal infections, yeast infections, allergic rashes, or bacterial infections.
Symptoms and signs of pustular psoriasis include at rapid onset of groups of small bumps filled with pus on the torso. Patients are often systemically ill and may have a fever.
Erythrodermic psoriasis appears as extensive areas of red skin often involving the entire skin surface. Patients may often feel chilled.
Scalp psoriasis may look like severe dandruff with dry flakes and red areas of skin. It can be difficult to differentiate between scalp psoriasis and seborrheic dermatitis when only the scalp is involved. However, the treatment is often very similar for both conditions.
How do health care professionals diagnose psoriasis?
The diagnosis of psoriasis is typically made by obtaining information from the physical examination of the skin, medical history, and relevant family health history.
Sometimes lab tests, including a microscopic examination of skin cells obtained from a skin biopsy, may be necessary.
Eczema vs. psoriasis
Occasionally, it can be difficult to differentiate eczematous dermatitis from psoriasis. This is when a biopsy can be quite valuable to distinguish between the two conditions. Of note, both eczematous dermatitis and psoriasis often respond to similar treatments. Certain types of eczematous dermatitis can be cured where this is not the case for psoriasis.
How many people have psoriasis?
Psoriasis is a fairly common skin condition and is estimated to affect approximately 1%-3% of the U.S. population. It currently affects roughly 7.5 million to 8.5 million people in the U.S. It is seen worldwide in about 125 million people. Interestingly, African Americans have about half the rate of psoriasis as Caucasians.
Picture of plaque psoriasis on the elbows. Source: Bigstock.com. Picture of psoriasis on the hands. Source: iStock.com.
Is psoriasis contagious?
No. A person cannot catch it from someone else, and one cannot pass it to anyone else by skin-to-skin contact. Directly touching someone with psoriasis every day will never transmit the condition.
Is there a cure for psoriasis?
No, psoriasis is not currently curable. However, it can go into remission, producing an entirely normal skin surface. Ongoing research is actively making progress on finding better treatments and a possible cure in the future.
Is psoriasis hereditary?
Although psoriasis is not contagious from person to person, there is a known hereditary tendency. Therefore, family history is very helpful in making the diagnosis.
What health care specialists treat psoriasis?
Dermatologists are doctors who specialize in the diagnosis and treatment of psoriasis, and rheumatologists specialize in the treatment of joint disorders and psoriatic arthritis. Many kinds of doctors may treat psoriasis, including dermatologists, family physicians, internal medicine physicians, rheumatologists, and other medical doctors. Some patients have also seen other allied health professionals such as acupuncturists, holistic practitioners, chiropractors, and nutritionists.
The American Academy of Dermatology and the National Psoriasis Foundation are excellent sources to help find doctors who specialize in this disease. Not all dermatologists and rheumatologists treat psoriasis. The National Psoriasis Foundation has one of the most up-to-date databases of current psoriasis specialists.
It is now apparent that patients with psoriasis are prone to a variety of other disease conditions, so-called comorbidities. Cardiovascular disease, diabetes, hypertension, inflammatory bowel disease, hyperlipidemia, liver problems, and arthritis are more common in patients with psoriasis. It is very important for all patients with psoriasis to be carefully monitored by their primary care providers for these associated illnesses. The joint inflammation of psoriatic arthritis and its complications are frequently managed by rheumatologists.
What are psoriasis treatment options?
There are many effective psoriasis treatment choices. The best treatment is individually determined by the treating doctor and depends, in part, on the type of disease, the severity, and amount of skin involved and the type of insurance coverage.
For mild disease that involves only small areas of the body (less than 10% of the total skin surface), topical treatments (skin applied), such as creams, lotions, and sprays, may be very effective and safe to use. Occasionally, a small local injection of steroids directly into a tough or resistant isolated psoriatic plaque may be helpful.
For moderate to severe psoriasis that involves much larger areas of the body (>10% or more of the total skin surface), topical products may not be effective or practical to apply. This may require ultraviolet light treatments or systemic (total body treatments such as pills or injections) medicines. Internal medications usually have greater risks. Because topical therapy has no effect on psoriatic arthritis, systemic medications are generally required to stop the progression to permanent joint destruction.
It is important to keep in mind that as with any medical condition, all medicines carry possible side effects. No medication is 100% effective for everyone, and no medication is 100% safe. The decision to use any medication requires thorough consideration and discussion with your health care provider. The risks and potential benefit of medications have to be considered for each type of psoriasis and the individual. Of two patients with precisely the same amount of disease, one may tolerate it with very little treatment, while the other may become incapacitated and require treatment internally.
A proposal to minimize the toxicity of some of these medicines has been commonly called "rotational" therapy. The idea is to change the anti-psoriasis drugs every six to 24 months in order to minimize the toxicity of one medication. Depending on the medications selected, this proposal can be an option. An exception to this proposal is the use of the newer biologic medications as described below. An individual who has been using strong topical steroids over large areas of their body for prolonged periods may benefit from stopping the steroids for a while and rotating onto a different therapy.
What creams, lotions, and home remedies are available for psoriasis?
Topical (skin applied) treatments include topical corticosteroids, vitamin D analogue creams like calcipotriene (Calcitrene, Dovonex, Sorilux), topical retinoids (tazarotene [Tazorac]), moisturizers, topical immunomodulators (tacrolimus and pimecrolimus), coal tar, anthralin, and others.
- Topical corticosteroids (steroids, such as hydrocortisone) are very useful and often the first-line treatment for limited or small areas of psoriasis. These come in many preparations, including sprays, liquid, creams, gels, ointments, and foams. Steroids come in many different strengths, including stronger ones that are used for elbows, knees, and tougher skin areas and milder ones for areas like the face, underarms, and groin. These are usually applied once or twice a day to affected skin areas. Strong steroid preparations should be limited in use. Overuse or prolonged use may cause problems, including potential permanent skin thinning and damage called atrophy.
- Calcipotriene cream is useful in psoriasis because of its effect on calcium metabolism. The advantage of calcitriol is that it is not known to thin the skin like topical steroids. There is a newer combination preparation of calcipotriene and a topical steroid called Taclonex. Not all patients may respond to calcipotriene. Prolonged use of these types of medications on more than 20% of the skin surface can produce an abnormal rise in body calcium levels.
- Moisturizers, especially with therapeutic concentrations of salicylic acid, lactic acid, urea, and glycolic acid may be helpful in psoriasis. These moisturizers are available as prescription and nonprescription forms. These help reduce the scales that impede the movement of topical medications into the deeper layers of the skin. Some available preparations include salicylic acid (Salex) and lactic acid (AmLactin, Lac-Hydrin). These may be used one to three times a day on the body. Other bland moisturizers, including Vaseline and Crisco vegetable shortening, may also be helpful in at least reducing the dry appearance of psoriasis.
- Immunomodulators (tacrolimus and pimecrolimus) have also been used with some limited success in mild psoriasis. These have the advantage of not causing skin thinning. They may have other potential side effects, including skin infections and possible malignancies (cancers). The exact association of these immunomodulator creams and cancer is controversial.
- Bath salts or bathing in high-salt-concentration waters like the Dead Sea in the Middle East along with careful exposure to sunlight can be beneficial to psoriasis patients.
- Coal tar is available in multiple preparations, including shampoos, bath solutions, and creams. Coal tar may help reduce the appearance and decrease the flakes in psoriasis. The odor, staining, and overall messiness with coal tar may make it less desirable than other therapies. A major advantage with tar is lack of skin thinning.
- Anthralin is available for topical use as a cream, ointment, or paste. The stinging, possible irritation, and skin discoloration may make this less acceptable to use. Anthralin may be applied for 10-30 minutes to psoriatic skin.
Quick GuidePsoriasis Types, Images, Treatments
Are psoriasis shampoos available?
Coal tar shampoos are very useful in controlling psoriasis of the scalp. Using the shampoo daily can be very beneficial adjunctive therapy. There are a variety of over-the-counter shampoos available without a prescription. There is no evidence that one shampoo is superior to another. Generally, the selection of a tar shampoo is simply a matter of personal preference.
What oral medications are available for psoriasis?
Oral medications include methotrexate (Trexall), acitretin (Soriatane), cyclosporine (Neoral), apremilast (Otezla), and others. Oral prednisone (corticosteroid) is generally not used in psoriasis and may cause a disease flare-up if administered.
- Acitretin (Soriatane) is an oral drug used for certain types of psoriasis. It is not effective in all types of the disease. It may be used in males and females who are not pregnant and not planning to become pregnant for at least three years. The major side effects include dryness of skin and eyes and temporarily elevated levels of triglycerides and cholesterol (fatty substance) in the blood. Blood tests are generally required before starting this therapy and are needed periodically to monitor triglyceride levels. Patients should not become pregnant while on this drug and usually avoid becoming pregnant for at least three years after stopping this medication.
- Cyclosporine is a potent immunosuppressive drug used for other medical uses, including organ transplantation. It may be used for severe, difficult-to-treat cases of widespread psoriasis. Improvement and results may be very rapid in onset. It may be hard to get someone off of cyclosporine without flaring their psoriasis. Because of the potential cumulative toxicity, cyclosporine should not be used for more than one to two years for most psoriasis patients. Major possible side effects include kidney and blood-pressure problems.
- Methotrexate is a common drug used for rheumatoid arthritis, and it has been used effectively for many years in psoriasis. It is usually given in small weekly doses (5 mg-25 mg), either orally or by injection. Blood tests are required before and during therapy. The drug may cause liver and lung damage. Close physician monitoring and monthly to quarterly visits and labs are generally required.
- FDA has approved a new oral drug, apremilast (Otezla), to treat psoriasis and psoriatic arthritis, with an entirely novel mode of action (inhibition of an enzyme, phosphodiesterase 4) and does not require intensive laboratory monitoring.
Subscribe to MedicineNet's Skin Care & Conditions Newsletter
What injections or infusions are available for psoriasis?
Recently, a new group of drugs called biologics have become available to treat psoriasis and psoriatic arthritis. They are produced by living cells cultures in an industrial setting. They are all proteins and therefore must be administered through the skin because they would otherwise be degraded during digestion. All biologics work by suppressing certain specific portions of the immune inflammatory response that are overactive in psoriasis. A convenient method of categorizing these drugs is on the basis of their site of action:
- Tumor necrosis factor-alpha (TNF-α) inhibitors (certolizumab pegol [Cimzia], etanercept [Enbrel], adalimumab [Humira], infliximab [Remicade], golimumab [Simponi])
- Interleukin 12 and 23 (IL-12/23) inhibitor (ustekinumab [Stelara])
- Interleukin 17 (IL-17) inhibitors (secukinumab [Cosentyx], brodalumab [Siliq], ixekizumab [Taltz])
- Interleukin 23 (IL-23) inhibitor (guselkumab [Tremfya])
- T cell inhibitor abatacept (Orencia)
Drug choice can be complicated, and your physician will help in selecting the best option. In some patients. it may be possible to predict drug efficacy on the basis of a prospective patient's genetics. It appears that the presence of the HLA-Cw6 gene is correlated with a beneficial response to ustekinumab.
Newer drugs are in development and no doubt will be available in the near future. As this class of drugs is fairly new, ongoing monitoring and adverse effect reporting continues and long-term safety continues to be monitored. Biologics are all comparatively expensive especially in view of the fact they none of them are curative. Recently, the FDA has attempted to address this problem by permitting the use of "biosimilar" drugs. These drugs are structurally identical to a specific biologic drug and are presumed to produce identical therapeutic responses in human beings to the original, but are produced using different methodology. Biosimilars ought to be available at some fraction of the cost of the original. If this will be an effective approach remains to be seen. The only biosimilar available currently is infliximab (Inflectra). Two other biosimilar drugs have been accepted by the FDA, an etanercept equivalent (Erelzi) and an adalimumab equivalent (Amjevita) -- but currently, neither are available.
Some biologics are to be administered by self-injections for home use while others are given by intravenous infusions in the doctor's office. Biologics have some screening requirements such as a tuberculosis screening test (TB skin test or PPD test) and other labs prior to starting therapy. As with any drug, side effects are possible with all biologic drugs. Common potential side effects include mild local injection-site reactions (redness and tenderness). There is concern of serious infections and potential malignancy with nearly all biologic drugs. Precautions include patients with known or suspected hepatitis B infection, active tuberculosis, and possibly HIV/AIDS. As a general consideration, these drugs may not be an ideal choice for patients with a history of cancer and patients actively undergoing cancer therapy. In particular, there may be an increased association of lymphoma in patients taking a biologic.
Biologics are expensive medications ranging in price from several to tens of thousands of dollars per year per person. Their use may be limited by availability, cost, and insurance approval. Not all insurance drug plans fully cover these drugs for all conditions. Patients need to check with their insurance and may require a prior authorization request for coverage approval. Some of the biologic manufacturers have patient-assistance programs to help with financial issues. Therefore, choice of the right medication for your condition depends on many factors, not all of them medical. Additionally, convenience of receiving the medication and lifestyle affect the choice of the right biologic medication.
Is there an anti-psoriasis diet?
Most patients with psoriasis seem to be overweight. Since there is a predisposition for those patients to develop cardiovascular disease and diabetes, it is suggested strongly that they try to maintain a normal body weight. Although evidence is sparse, it has been suggested that slender patients are more likely to respond to treatment.
Although dietary studies are notoriously difficult to perform and interpret, it seems likely that an anti-inflammatory diet whose fat content is composed of polyunsaturated oils like olive oil and fish oil is beneficial for psoriasis. The so-called Mediterranean diet is an example.
What about light therapy for psoriasis?
Light therapy is also called phototherapy. There are several types of medical light therapies that include PUVA (an acronym for psoralen + UVA), UVB, and narrow-band UVB. These artificial light sources have been used for decades and generally are available in only certain physician's offices. There are a few companies who may sell light boxes or light bulbs for prescribed home light therapy.
Natural sunlight is also used to treat psoriasis. Daily short, controlled exposures to natural sunlight may help or clear psoriasis in some patients. Skin unaffected by psoriasis and sensitive areas such as the face and hands may need to be protected during sun exposure.
There are also multiple newer light sources like lasers and photodynamic therapy (use of a light activating medication and a special light source) that have been used to treat psoriasis.
PUVA is a special treatment using a photosensitizing drug and timed artificial-light exposure composed of wavelengths of ultraviolet light in the UVA spectrum. The photosensitizing drug in PUVA is called psoralen. Both the psoralen and the UVA light must be administered within one hour of each other for a response to occur. These treatments are usually given in a physician's office two to three times per week. Several weeks of PUVA is usually required before seeing significant results. The light exposure time is gradually increased during each subsequent treatment. Psoralens may be given orally as a pill or topically as a bath or lotion. After a short incubation period, the skin is exposed to a special wavelength of ultraviolet light called UVA. Patients using PUVA are generally sun sensitive and must avoid sun exposure for a period of time after PUVA. Common side effects with PUVA include burning, aging of the skin, increased brown spots called lentigines, and an increased risk of skin cancer, including melanoma. The relative increase in skin cancer risk with PUVA treatment is controversial. PUVA treatments need to be closely monitored by a physician and discontinued when a maximum number of treatments have been reached.
Narrow-band UVB phototherapy is an artificial light treatment using very limited wavelengths of light. It is frequently given daily or two to three times per week. UVB is also a component of natural sunlight. UVB dosage is based on time and exposure is gradually increased as tolerated. Potential side effects with UVB include skin burning, premature aging, and possible increased risk of skin cancer. The relative increase in skin cancer risk with UVB treatment needs further study but is probably less than PUVA or traditional UVB.
Sometimes UVB is combined with other treatments such as tar application. Goeckerman is a special psoriasis therapy using this combination. Some centers have used this therapy in a "day care" type of setting where patients are in the psoriasis treatment clinic all day for several weeks and go home each night.
Recently, a laser (excimer laser XTRAC) has been developed that generates ultraviolet light in the same range as narrow-band ultraviolet light. This light can be beneficial for psoriasis localized to small areas of skin like the palms, soles, and scalp. It is impractical to use in in extensive disease.
What is the long-term prognosis with psoriasis? What are complications of psoriasis?
Overall, the prognosis for most patients with psoriasis is good. While it is not curable, it is controllable. As described above, recent studies show an association of psoriasis and other medical conditions, including obesity, diabetes, and heart disease.
Is it possible to prevent psoriasis?
Since psoriasis is inherited, it is impossible at this time to suggest anything that is likely to prevent its development aside from indulging in a healthy lifestyle.
What does the future hold for psoriasis?
Psoriasis research is heavily funded and holds great promise for the future. Just the last five to 10 years have produced great improvements in treatment of the disease with medications aimed at controlling precise sites of the process of inflammation. Ongoing research is needed to decipher the ultimate underlying cause of this disease.
Is there a national psoriasis support group?
Yes, the National Psoriasis Foundation (NPF) is an organization dedicated to helping patients with psoriasis and furthering research in this field. They hold national and local chapter meetings. The NPF web site (http://www.psoriasis.org/home/) shares up-to-date reliable medical information and statistics on the condition.
Where can people get more information on psoriasis?
A dermatologist, the American Academy of Dermatology at http://www.AAD.org, and the National Psoriasis Foundation at http://www.psoriasis.org/home/ may be excellent sources of more information.
There are many ongoing clinical trials for psoriasis all over the United States and in the world. Many of these clinical trials are ongoing at academic or university medical centers and are frequently open to patients without cost.
Clinical trials frequently have specific requirements for types and severity of psoriasis that may be enrolled into a specific trial. Patients need to contact these centers and inquire regarding the specific study requirements. Some studies have restrictions on what recent medications have been used for psoriasis, current medication, and overall health.
Some of the many medical centers in the U.S. offering clinical trials for psoriasis include the University of California, San Francisco Department of Dermatology, the University of California, Irvine Department of Dermatology, and the St. Louis University Medical School.
Medically Reviewed on 2/1/2018
Alwan, W., and F.O. Nestle. "Pathogenesis and Treatment of Psoriasis: Exploiting Pathophysiological Pathways for Precision Medicine." Clin Exp Rheumatol 33 (Suppl. 93): S2-S6.
Arndt, Kenneth A., eds., et al. "Topical Therapies for Psoriasis." Seminars in Cutaneous Medicine and Surgery 35.2S Mar. 2016: S35-S46.
Conrad, Curdin, Michel Gilliet. "Psoriasis: From Pathogenesis to Targeted Therapies." Clinical Reviews in Allergy & Immunology Jan. 18, 2015.
Dowlatshahi, E.A., E.A.M van der Voort, L.R. Arends, and T. Nijsten. "Markers of Systemic Inflammation in Psoriasis: A Systematic Review and Meta-Analysis." British Journal of Dermatology 169.2 Aug. 2013: 266–282.
Greb, Jacqueline E., et al. "Psoriasis." Nature Reviews Disease Primers 2 (2016): 1-17.
National Psoriasis Foundation. "Systemic Treatments: Biologics and Oral Treatments." 1-25.
Ogawa, Eisaku, Yuki Sato, Akane Minagawa, and Ryuhei Okuyama. "Pathogenesis of Psoriasis and Development of Treatment." The Journal of Dermatology 2017: 1-9.
Villaseñor-Park, Jennifer, David Wheeler, and Lisa Grandinetti. "Psoriasis: Evolving Treatment for a Complex Disease." Cleveland Clinic Journal of Medicine 79.6 June 2012: 413-423.
Woo, Yu Ri, Dae Ho Cho, and Hyun Jeong Park. "Molecular Mechanisms and Management of a Cutaneous Inflammatory Disorder: Psoriasis." International Journal of Molecular Sciences 18 Dec. 11, 2017: 1-26.