Psoriasis is a common and lifelong skin disorder that causes thick crusty patches covered with white or silvery scales. It is a global health challenge, affecting over 125 million people worldwide. In Hong Kong, approximately 0.3% of the population, i.e. more than 20,000 people, are living with this disease. You may wonder why it affects relatively less people in Hong Kong compared to the world. The good news is that there are only 10 out of 44 known genes related to psoriasis are found in Chinese ethnicity.
What is Psoriasis?
Psoriasis is a chronic, autoimmune skin condition that increases the rate of skin cell production. The normal life cycle of skin cells is about one month. However in psoriasis, this process takes only less than a week, resulting in overproduction and buildup of cells on the skin surface. This is why raised red patches and thick scales that can be painful, itch, crack and flake off are commonly seen.
Locations, age prevalence and more
Psoriasis is typically present on elbows, knees and scalp, particularly at the hairline. It can also appear on the face, hands, neck, ear canals, nails and genital areas. In most cases, it only covers a few small areas, while it can be widespread for some people.
People at any age can develop psoriasis, however it is more common in people aged 15-25, and in their fifties. Generally speaking, psoriasis affects a larger area and brings more serious impacts if it starts earlier in life. Psoriasis is not contagious. Both men and women carry an equal risk of getting it.
Until now, there is no complete cure but it is controllable. Psoriasis comes and goes. Sometimes the symptoms can be severe, then they may disappear before flaring up again.
Psoriasis vs Eczema
It can be hard to tell psoriasis and eczema apart as some of their symptoms overlap. However, the former is usually characterized by thick patches with flaking white scales. The boundary of the patches are sharply demarcated. As for eczema, it mostly presents as very dry skin with thinner red patches with ill-defined edges. Oozing can occur sometimes. The locations of affected skin areas are different as well. Click here to learn more about eczema.
Types of Psoriasis
Psoriasis comes in many types. Although people commonly only have one type at a time, it is possible for two types to appear simultaneously.
- Plaque psoriasis: It is the most common type (80%-90% globally, 60%-70% in Hong Kong). One feature is red oval, clearly outlined plaques of inflamed skin that covered in dry silver scales. They tend to develop symmetrically over the body.
- Guttate psoriasis: Instead of patches, they occur in small red water drop-like spots and are more common in children and young adults.
- Inverse/ flexural psoriasis: It causes red, smooth, non-scaling patches in skin areas such as the armpits, groin, genitals and buttocks crease.
- Pustular psoriasis: Sore painful lesions with pus mostly develop on the palms of the hands and soles of the feet.
- Generalized pustular psoriasis: It is fast-developing and occurs suddenly. A large area of skin becomes red, tender and dry. The fluid-filled bumps re-appear every few days or weeks in cycles.
- Erythrodermic psoriasis: It is severe and life-threatening. Most of the skin is red and looks burnt.
- Psoriatic arthritis: Joints are involved, indicating that psoriasis is serious and cannot be cured. One may notice swelling and pain in a finger or toe. Research found that 10%-30% of people with psoriasis will develop it.
Signs and Symptoms
The signs and symptoms of psoriasis vary with the type, locations and area involved. The most common ones are:
- Red plaques of inflamed skin with white or silvery scales
- Scales can shed easily, and patches may merge
- Dry skin that may bleed if it is cracked
- Sore, itchy and painful patches
- Thickening and pitting of nails
- Swollen and painful joints
Causes and risk factors
The exact causes of psoriasis are still unclear. However, it is largely related to issues in the immune system. T cells, a type of white blood cells, target and kill the normal skin cells wrongly. This speeds up the growth rate of skin cells. The new ones push themselves upwards while the falling off of old skin cells cannot catch up with the production pace. This results in accumulation and formation of thick patches with scales.
Other risk factors and triggers include:
- Genetics: nearly 50% of psoriatic patients have family members with the condition.
- Medication: e.g. lithium, beta blockers (e.g. atenolol, propranolol), corticosteroids (e.g. prednisolone, fluocinolone), indomethacin, and antimalarials (e.g. atovaquone). They make your psoriasis worse.
- Skin injuries and skin conditions: it is known as Koebner phenomenon,where psoriasis occurs after sunburn, bites, cuts, tattoos and blisters, etc.
- Hormone changes: especially in women during puberty and menopause, who may experience a flare up.
- Alcohol: men are at a greater risk if they consume alcohol excessively.
- Smoking: smokers are more likely to develop and have more severe condition that is less responsive to treatment.
- Emotional stress: it affects the immune system, so you become more vulnerable to psoriasis.
- Infections: both bacterial and viral infections, in particular HIV infection and strep throat, increase the risk.
- Sunlight: although many people find improvement in symptoms after sun exposure, beware of sunburns which is a trigger of psoriasis.
- Obesity: people with excess weight tend to have more skin folds and creases where psoriasis can develop.
Complications of Psoriasis
Psoriasis is often associated with the following complications:
- Eye disorders: e.g. inflammation of the eyelids and the conjunctiva.
- Type 2 diabetes: it is well known that type 2 diabetes is common in psoriatic patients.
- Cardiovascular diseases: research has established a relationship between heart attacks and psoriasis. Other diseases include, peripheral artery disease, hypertension and high cholesterol.
- Autoimmune diseases: e.g. inflammatory bowel disease and celiac disease.
Kidney disease: people with psoriasis are at increased risk of getting it.
Psychological problems: e.g. anxiety, depression and disrupted social activities probably due to poor management and self-image.
- Parkinson’s disease: Studies found that the ratio of developing parkinson’s disease in people with and without psoriasis is 1.38.
Diagnosis of Psoriasis
Your doctor may diagnose psoriasis by either physical examination or microscopic examination of a sample of the affected skin. He/she may also review your family history as it is one of the risk factors, and ask you some questions to find out any possible triggers.
How to treat Psoriasis
Treatment options depend on the type, location and severity which can be mild (<3% of body surface is affected), moderate (3%-10%)or severe (>10%). They do not provide a cure but still can be effective.
Topical agents (for mild and moderate disease)
- Corticosteroids: they reduce inflammation and control itchiness. They come in various strength and long-term use causes a number of side effects, for example skin thinning.
- Vitamin D analogues: they work by decreasing skin cell production. Examples include calcipotriene (Dovonex) and calcitriol (Vectical).
- Coal tar: it is a thick heavy oil and a derivative of coal. It reduces proliferation of keratinocytes, and therefore improve itching and scaling. However, it can stain skin and clothing, and cause folliculitis.
- Anthralin: it slows down skin cell growth to smoothen skin. However, it can cause skin irritation and staining of skin and clothing.
- Retinoids: they are derived from vitamin A. They remove scales by slowing skin cell production. However, skin may become more sensitive to sunlight after use.
- Salicylic acid: it promotes shedding of scales.
- Emollients: they are for lubrication to soothe dryness, cracking and scales.
Systemic agents (for moderate to severe disease)
- Cytotoxic drugs: they reduce inflammation by curbing T cell activity in the skin. Methotrexate is often used. It can also alleviate psoriatic arthritis.
- Retinoids: one common oral retinoids is acitretin (Soriatane). Careful consideration and consultation with doctor is needed as this class of drugs causes serious malformations in babies. Pregnant women and those who plan to get pregnant should avoid them.
- Immunosuppressants: for example cyclosporine. They work by suppressing the immune system. Caution with the risk of developing infections.
Phototherapy is exposing our skin regularly to ultraviolet light to treat moderate to severe psoriasis. Psoralen (a naturally-occurring substance in many plants that absorbs UV light) with ultraviolet A (PUVA), UVB and narrow-band UVB therapy are available. UVB can be used in a combined treatment with coal tar.
They are a new class or drugs reserved for patients unresponsive to other treatments. They can be very effective but expensive. They target substances involved in inflammation.
What doctors to see for Psoriasis
Apart from visiting dermatologist for psoriasis as it is a skin disease, there are also other specialists you can see to help improve your symptoms, for example a rheumatologist.
A rheumatologist is a licensed medical doctor specializing in rheumatic diseases i.e. diseases of the joints, bones and muscles. One common type of psoriasis is psoriatic arthritis, so a rheumatologist can provide professional treatment and advice in managing it.
An internist is similar to a general physician but receives more specialized training. They can also provide diagnosis and treatment for other health issues related to psoriasis.
Sometimes patients may need a psychologist to take care of their mental health as psoriasis affects appearance that could affect one’s self-image and self-esteem, affecting mental well-being if it is not managed properly in the long run.
Useful Resources in Hong Kong
- My Psoriasis Hong Kong
- Hong Kong Psoriasis Patients Association (Chinese only)
- Hong Kong Psoriatic Arthritis Association (Chinese only)
This article was medically reviewed by Dr. Nicola Chan 陳珮瑤醫生 on July 29, 2019. Dr. Nicola Chan is a Specialist in Dermatology in private practice, based in Hong Kong. She graduated from the University of Cambridge, UK, and received post-graduate medical training in Cambridge, London and Hong Kong. This was followed by further laser and aesthetic dermatology training in Boston and Baltimore, USA. Dr. Chan is a member of the Hong Kong Society of Dermatology and Venereology, American Society of Laser Medicine and Surgery, Asian Dermatological Association, and Hong Kong College of Dermatologists.