Psoriasis

PKGhatak, MD

Psoriasis is a skin disease that manifests as red, itchy scaly patches. Psoriatic lesions commonly appear over the knees, elbows, trunk and scalp. Psoriasis patches can range from a few spots of dandruff-like lesions to scaling lesions covering a large area of the body.

Types of psoriasis:

For descriptive purposes the psoriatic lesions are called:

Plaque psoriasis, Nail Psoriasis, Guttate psoriasis, Inverse psoriasis, Pustular psoriasis, Erythrodermic psoriasis, and Psoriatic arthritis.

The most common type of psoriasis is plaque psoriasis.

What causes psoriasis.

It is a multifactorial disorder caused by an interaction between Inherited Genetic Mutations and environmental risk factors. The abnormal Immune reaction manifested by very rapid turnover of skin cells, dead skin shedding lags behind the new cells generated resulting in itching and redness of the skin.

What are the risk factors.

Some of the known triggers are – Streptococcal infection of the skin and throat, dry and cold weather, cuts and bruises of the skin, insect bites, stress, certain medications like - antimalaria drugs, High BP drugs, lithium, etc., sunburns, and rapid withdrawal of prednisone.

Is vaccination safe in Psoriasis.

Childhood vaccination should proceed as usual. All vaccinations, skin injury, and surgery may produce a flare up of psoriasis, this is known as Kobener Phenomenon.

What genetic mutations are associated with Psoriasis.

Genome-wide association studies have identified more than 60 susceptibility regions, those genes are related to Thymic 17(Th-17) cell action. Interleukin -36(IL-36) is an important amplifier of Th- 17 signaling.

In addition, Linkage analysis identified 9 different regions - known as PSORS 1 to PSORS 9 - associated with psoriasis.

In North American PSORS 2 is identified as a common variant and psoriasis is inherited as an Autosomal Dominant condition. Mutation of CARD 14 gene identified as the molecular defect underlying cause of psoriasis. Card 14 encodes an adaptor protein that is highly expressed in skin cells known as keratinocytes.

In worldwide studies, PSORS1 locus maps detected an association of PSORS1 to the Major Histocompatibility Complex (CHC) on chromosome 6p21.

Signs and symptoms of psoriasis.

Psoriasis is a chronic remitting skin disease, generally worse in the winter months and improves in summer. About 8 million people in the USA have psoriasis; 40 % of them may also develop arthritis.

Psoriatic skin lesions appear as red patches of skin with thick silvery scales. Psoriasis may appear as raised red or pink plaques with silvery scales called guttate psoriasis. Guttate psoriasis is common in children. In addition, the flowing symptoms and signs may be present.

Dry, cracked skin that may bleed or itch.

Itching, burning, or soreness.

Thickened, pitted, or ridged nails.

Swollen and stiff joints in Psoriatic arthritis. The clinical picture of psoriatic arthritis resembles Rheumatoid arthritis; arthritis may precede skin lesions and over time becomes resistant to therapy.

Treatment of Psoriasis.

It can be discussed in three categories.

1. Topical 2. Phototherapy, 3. Systemic.

Topical.

Emollients.

Local skin emollients are moisturizers and are effective in early cases involving limited areas of the body. It retains moisture in the skin thereby reducing itching and scaling.

Hydrocortisone cream/ointment.

Steroid creams of various strengths are available by prescription and the over the counter1% hydrocortisone creams are useful for reducing irritated skin lesions and reduces flaking and itching.

Vitamin D analogs.

It slows down skin cell production and has an anti-inflammatory effect. The ointment can be used on the scalp, trunk, limbs are other areas.

Calcineurin inhibitors.

Several compounds are available. They reduce immune reactions. And produce remission of skin lesions, and is useful in lesions over sensitive areas of the body and also the scalp.

Coal tar.

Heavy oil obtained from coal processing is effective in psoriasis. The mechanism of action is unknown. The oil has an odor and can stain clothing and bedding.

Dithranol.

It is used only under medical supervision. Dithranol ointment can be applied over a wide area and allowed to act for 10 to 60 minutes then washed off. It may burn the skin if used inappropriately.

Phototherapy.

Special light therapy centers use various forms of light therapy. A wide area of the body can be treated. Each session lasts only a few minutes but is repeated 3 -4 times a week and stretched over 6 to 8 weeks. UVB light is invisible to the eyes and is commonly used in phototherapy. Phototherapy can be combined with Dithranol and Coal tar skin ointment.

Phototherapy is effective when other treatments fail.

PUVA.

Psoralen is combined with Ultra Violet A light.

This combination makes the UV A light pernitrates deep into the skin. It is useful in cases where other forms of therapy have failed. But repeated use may cause skin cancer.

Systemic therapy.

Drugs are classified as Non-Biological and Biological agents.

Non-Biological.

All these drugs are useful in reducing skin cell proliferation, controlling inflammation, itching, and scaling. Many of them also have significant side effects that require regular follow ups.

Methotrexate.

Initially, the methotrexate is administered IM injections, then switched to oral therapy. Usually given once a week, periodic blood count and renal function are checked for side effects.

Cyclosporine.

This medication is an anti-rejection drug; newer drugs of this category are Sirolimus and Tacrolimus. Drugs are given orally and also locally on the skin as an ointment. Blood levels of these drugs are checked to adjust the dose to keep in the therapeutic range. All of these drugs are useful in suppressing immune reactions.

Acitretin.

It is a retinoid compound and be taken orally. It is widely used but also has side effects including liver damage.

Apremilast.

Apremilast is a Phosphodiesterase inhibitor and the pill is taken by mouth daily. It is effective in both skin lesions and psoriatic arthritis.

Dimethyl fumarate.

This drug is primarily used in Multiple sclerosis. It is also used in Psoriasis.

Biological agents.

Bioactive immunosuppressants are given by injections. Each drug is administered by a given protocol. If significant improvement of psoriasis is not seen in 8 to 12 weeks, then these drugs are discontinued. Since these are used in advanced and resistant cases, the outcomes of use in psoriasis are also variable.

Commonly used biological drugs are -

Etanercept. Administered weekly by IM injection.

Adalimumab. Given every 2 weeks by injection.

Infliximab. Given by intravenous injection.

Ustekinumab. This drug can the given subcutaneously or by IV infusions. Usually given every 4 weeks. It is effective in severe plaque psoriasis.

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Psoriasis  usually appears as red or pink plaques of raised, thick, scaly skin. However, it can also appear as small, flat bumps or large, thick plaques