Psoriasis

Topic Highlights

●   Psoriasis is a chronic skin disease that can affect one's quality of life, it occurs when the body's immune system sends out faulty signals that speed up the growth cycle of skin cells.  

●   It is characterized by the appearance of scaly patches or 'plaques' on the skin ' usually on the elbow or knee, due to excessive skin production.  

●   This visual presentation focuses on skin anatomy, pathophysiology of psoriasis, its types, symptoms, treatment options and self help.  

●   The presentation also discusses psoriatic arthritis.  

Transcript

Psoriasis is a chronic disease of the skin and the joints. It is an uncomfortable chronic cutaneous disease that affects the ability to function. Psoriatics often suffer from psychological and emotional distress because the disease impacts their physical appearance. Psoriasis affects 2-3 percent of the world's population. Its onset usually occurs after puberty.

The skin consists of three layers, the epidermis, dermis and subcutaneous fat. The epidermis is the visible layer of the skin that consists of several layers of cells arranged on top of one another. New layers of cells continue to develop from the bottom of the epidermis and rise to the top in a process called turnover. In a continuous cycle, skin cells slough off and are replaced by newer layers. Normally this cycle takes about 3-4 weeks. This layer provides a tough, flexible and waterproof covering for the body.

The middle layer is the dermis. It consists of collagen and ground substances. Hair follicles are present in the dermis; sebaceous (oil) glands and apocrine (scent) glands are associated with these follicles. While sweat glands help to regulate body temperature, and nerve endings convey the sensations of pain, itching, touch, or temperature to the brain, the oil glands produce the sebum, which help to moisturize the skin. The deepest layer of the skin consists of fat.

The eruption of psoriasis is an inflammation in the dermis and a hyperproliferation of the epidermis. In this case the turnover takes 2-6 days, with these cells rising to the surface and an accumulation of both dead and live cells. Though the exact causes are not known, various theories have developed to explain the causes.

The primary pathologic process is immune mediated. It is believed that psoriasis is due to dysregulation of T cells. The etiology of psoriasis is barely understood. Recent findings suggest that the paradigm of Th1/Th2 of psoriasis is shifting towards Tregs and Th17.

Psoriasis has a genetic link. HIV infection may lead to a psoriasis flare up. While moderate exposure to sun may be beneficial, severe sunburn or prolonged exposure to certain chemicals may worsen psoriasis. Stress is also a risk factor. Other risk factors include skin trauma, medications such as lithium, beta-blockers, some of the anti-malarial drugs and anti-inflammatory drugs.

The majority of the people with psoriasis have comparatively mild cases of psoriasis. The symptoms of psoriasis vary depending on the type of psoriasis.

The most common type of psoriasis is plaque psoriasis, which accounts for about 80% cases. This type is characterized by dry, red, well-made plaques covered with flaky white scales. These plaques are commonly found on the elbows and knees. In more severe cases the trunk is involved, though they may appear on any part of the body. Plaques are well defined and vary in size. They may cause itching.

Guttate psoriasis is characterized by tear-shaped scaly papules. It usually occurs on the trunk, arms, or legs, though it may occur on other parts of the body. In some cases, the sores may disappear and never recur. Sometimes the recurrence may be triggered due to infections.

Some children may develop plaque psoriasis later in life. Infections such as streptococcal throat infection seem to trigger guttate psoriasis, especially in children and young adults. This form of psoriasis is relatively uncommon.

Pustular psoriasis is a life-threatening form of psoriasis characterized by pus-filled blisters or pustules. These pustules are sterile and tend to follow a pattern - the skin reddens followed by the appearance of pustules and scaling. The blisters are not infected but contain white blood cells. It may be generalized - covering large areas of the body or localized - occurring on hands, feet, fingers or toes.

Inverse psoriasis is characterized by moist erosions lacking scales found in skin folds such as armpits, groin, between the buttocks, under the breasts and around the genitals. These patches are sensitive to friction and sweating and may become irritated.

Nail psoriasis may occur alone or with plaque psoriasis in some people. It is characterized by small pits in the nails. In some cases it may cause the nail to separate from the nail bed. Nail psoriasis produces a variety of changes in the appearance of fingernails and toenails. These changes include discoloring under the nail plate, pitting of the nails, lines going across the nails, thickening of the skin under the nail, and the loosening (onycholysis) and crumbling of the nail.

Erythrodermic psoriasis is a very rare form of life threatening psoriasis. It is characterized by widespread inflammation, redness and scaling of the skin. It may be triggered by severe sunburn, oral steroids or other drugs. In rare cases severe inflammation may affect the body's ability to regulate temperature and fluid balance and can lead to death.

Patients with psoriasis are at risk for obesity. The reason for this is not understood and may have to do with the increased risk of depression and decreased physical activity that psoriatics suffer from.

Psoriatic arthritis is an aspect of psoriasis. It is found in nearly 30% of the people with psoriasis of the skin. Five types of psoriatic arthritis have been defined that can coexist but tend to occur separately in most cases.

Asymmetrical oligoarthritis (55-70%) is arthritis involving primarily the small joints of the fingers or toes and the distal interphalangeal joints.

Asymmetrical arthritis (30-50%) involves the joints of the extremities. This form is commonly associated with nail changes. Inflammation of these joints is not seen in rheumatoid arthritis.

Symmetrical polyarthritis (15-70%) resembles rheumatoid arthritis (RA), but with a negative rheumatoid factor. Patients with psoriasis, symmetric polyarthritis, and positive rheumatoid factor are considered to have rheumatoid arthritis and concomitant psoriasis.

Arthritis mutilans (3-5%) is rare but deforming and destructive. It involves arthritis of small joints of the hands and feet, with osteolysis; patients may have constitutional symptoms, usually associated with severe skin disease and sacroiliitis.

Psoriatic spondylitis (5-33%) or arthritis of the sacroiliac joints and spine may occur alone or with other forms of psoriatic arthritis. It’s often asymptomatic. Sacroiliitis is usually asymmetric, and syndesmophytes are usually bulky, nonmarginal, and discontinuous, as in reactive arthritis.

Other musculoskeletal features of psoriatic arthritis include dactylitis, tenosynovitis, and enthesitis. Dactylitis is the often painful swelling of fingers and toes. It occurs in more than 30% of patients. Dactylitis is not seen in rheumatoid arthritis. Tenosynovitis is the inflammation of synovium causing pain and swelling. Enthesitis is the inflammation at the insertion of tendons into bones.

Psoriasis is usually diagnosed with a visual examination and medical history. Sometimes, a skin biopsy may be needed to confirm the diagnosis. Radiologic studies of the joints may be taken to establish a diagnosis of psoriatic arthritis.

Psoriasis is usually graded as mild (affecting less than 3% of the body), moderate (affecting 3-10% of the body) or severe (greater that 10% body surface involvement).

Several scales exist for measuring the severity of psoriasis. The degree of severity is generally based on the following factors: the proportion of body surface area affected; disease activity (degree of plaque redness, thickness and scaling); response to previous therapies; and the impact of the disease on the person.

The Psoriasis Area Severity Index (PASI) is the most widely used measurement tool for psoriasis. PASI combines the assessment of the severity of lesions and the area affected into a single score in the range 0 (no disease) to 72 (maximal disease). The PASI can be too unwieldy to use outside of trials, which has led to attempts to simplify the index for clinical use.

Treatment for psoriasis depends on the type, location and severity. Topical treatments are the first line treatment for mild disease. A variety of topical creams can be directly applied to the skin to ameliorate psoriasis.

Vitamin D3 analogues such as calcipotriol may be used. Dithranol (Anthralin) is applied to the skin. It limits the extra rapid growth of skin cells. It is generally prescribed as a short contact treatment as it may irritate skin and even stain skin, hair and clothing. It is applied and then washed off after a short while. One of the advantages of anthralin over cortisone ointments is that once the psoriasis is under control, it does not recur for a long time. Taclonex, which is a combination of dovonex and betamethasone, is also effective for treatment of psoriasis.

Topical retinoids such as tazorac normalize DNA activity in skin cells. Retinoids are vitamin A derivatives, which bind to certain receptors in the skin cells and help reduce proliferation of skin cells and inflammation. Clobetasol propionate is a high potency corticosteroid, which is generally used for short-term treatment and is discontinued when adequate results have been achieved. It is available in a variety of formulations that include creams, ointments, foams, lotions and liquids.

Phototherapy is the first line of treatment for moderate to severe disease. Here the skin is exposed to ultraviolet rays. The patient enters a special light box wearing dark glasses and other protection and is exposed to these rays for a specific period of time. This may be done in combination with other treatments for better results. Smaller phototherapy units exist for home use.

The next step involves the use of medications, which are ingested orally or by injection. Retinoids such as acitretin may help reduce proliferation of skin cells. Retinoids may cause severe birth defects. Drugs such as Methotrexate may slow the progression of psoriatic arthritis and help reduce the turnover of skin cells. Long-term use or high dosage may cause serious side effects.

TNFα blockers, methotrexate or NSAIDS are used to treat psoriatic arthritis. NSAIDS or bactrim should not be used with methotrexate. Long-term use may cause serious side effects.

Adalimumab, infliximab (Anti-TNF drugs), PUVA and narrow band UVB are frequently used. Cyclosporine is a very effective drug for treating psoriasis. It suppresses the immune system and can be associated with side effects such as infections and other health problems.

Biologic drugs such as alefacept, efalizumab, infliximab, adalimumab and etanercept are used in the treatment of severe psoriasis. These drugs may be given intravenously or as intramuscular injection. These are generally prescribed for patients who do not respond to other medications or those with psoriatic arthritis. These work by affecting the immune system. Side effects include risk of infections.

One of the emerging theories supporting findings by dermatologists and immunologists is that a subcutaneous injection of monoclonal antibodies to interleukin-12/23 improves the treatment of psoriasis.

Exposure to sun may improve the skin condition. It is possible to live a productive life even with psoriasis. Those with psoriasis should talk to co-workers and family members about the problem and let them know that it is not contagious. They should also talk to a friend or counselor to help cope with the depression or emotional trauma that psoriasis can cause.