Skin is the largest organ in the human body. it covers almost all the external surfaces of our bodies. Skin acts as an active shield against germs and pathogens. Without such a barrier, human bodies will be exposed to more infections. Skin also regulates our temperature by acting as a thermal insulator in cold weather and by sweating to reduce body temperature in hot weather. Skin is formed from two main layers called the outer epidermis and inner dermis. The dermis is much thicker than the epidermis as it forms about 90% of the skin thickness. Therefore, the dermis contains blood vessels and most skin appendages such as hair follicles, sweat glands, and sebaceous glands.
Both layers are important and perform different functions. However, only the outer epidermis is capable of regeneration. For instance, if a group of cells in the epidermis is injured and died, the surrounding cells will divide and restore the dead tissue with a new one, whereas the dermis cannot regenerate its dead cells.
In fact, the process of regeneration is not only active when the skin is cut but it is a non-stopping process with the invisible shedding of dead cells to make the epidermis perform its functions properly. The epidermal cells divide and regenerate at a certain rate as it is believed that a new layer of cells is proliferated every month. The epidermis is estimated to turnover completely every 50 days on average. If the skin is cut deep enough to injure the dermis, the body replaces the dead cells in the dermis with fibrous tissue that forms a scar.
Definition & Lesion Description
What is psoriasis? Psoriasis is a chronic inflammatory disease of the skin affecting almost any part of the body. Unlike other skin diseases, psoriasis isn’t contagious and can’t be transmitted in any known way. Psoriatic lesions have characteristic morphological features as they appear as pink, itchy, dry, and well-defined plaques that are usually covered with silvery-white scales.
No one can tell for sure what causes psoriasis; however, many doctors suppose it is caused by overactive immune responses. Microscopic examination of the skin with psoriasis revealed that whatever initiated psoriasis resulted in over-proliferation (cell division) of the epidermis to be up to 10 times the normal growth rate. The accelerated rate of cell division leads to the proliferation of under-mature cells with poor structure and abnormal keratinization.
Clinical presentation of psoriasis usually includes sudden development of pink scaly plaques over the most exposed areas to traumas such as extensor surfaces of the arm, legs, and scalp. The psoriatic plaques could get itchy, especially during flare-ups. If patients try to remove the scales manually, this will lead to an eruption of multiple bleeding spots. Due to a lack of curative treatment, psoriasis tends to have a chronic course with seasonal fluctuations.
Psoriasis often does not have a stationary course, but it flares up in attacks of exacerbation followed by remission. Doctors noticed an unexplained phenomenon associated with psoriasis called the Koebner phenomenon as patients usually complain of the development of trauma-induced psoriatic lesions in previously healthy areas of the skin.
Types of Psoriasis
Psoriasis, for an unknown reason, has different manifestations and clinical presentations upon which psoriasis is divided into 6 main subtypes. These types are the following:
1) Psoriasis Vulgaris (Plaque Psoriasis)
It is the most common type of psoriasis as it is estimated to represent about 80% of patients with psoriasis. For such reason, its name was derived from “Vulgaris” (a Latin adjective that means common). Psoriasis Vulgaris manifest with the typical presentation of psoriasis, which is an acute eruption of pink, dry, oval plaques covered with silvery-white scales. These plaques may be itchy and tend to flare up in the winter due to skin dryness. Psoriasis Vulgaris may appear anywhere on the skin, yet it is more frequently seen over the knee, scalp, face, the extensor surfaces of the arm and leg.
Small pitting depressions and distinctive reddish-brown staining of the nail bed surface, which resembles an oil stain, are common nail signs associated with psoriasis Vulgaris. Nail pitting and ridging accompanied with psoriasis is believed to affect up to 40% of psoriatic patients. You may also notice an accumulation of keratotic material below the nails that may lead to nail partial separation from the underlying skin. Mucous membranes such as oral and nasal cavities are rarely affected by psoriasis Vulgaris.
2) Intertriginous (Inverse) Psoriasis
It is a type of psoriasis that affect the intertriginous and flexural regions of the body such as armpits, groins, buttocks, and sub-mammary areas. Skin lesions of Intertriginous psoriasis may have the same microscopic characteristics as psoriasis Vulgaris, but they don’t look the same to the naked eye. Intertriginous psoriasis appears as red moist plaques with no scales because of sweating and maceration.
3) Pustular Psoriasis
It is a less common type of psoriasis that appears as multiple small pus-filled bumps (pustules). This condition usually affects the palms and soles. In rare cases, pustular psoriasis spread and gets disseminated all over the body in a condition called generalized pustular psoriasis which has a considerable mortality rate and needs urgent medical attention.
4) Guttate Psoriasis (Raindrop Psoriasis)
It is so named as it manifests itself as numerous pink scaly spots. Guttate psoriasis often spares palms and soles and affects the trunk, upper arms, and thighs. Unlike Psoriasis Vulgaris, it has a low prevalence estimated to be less than 2% of psoriatic patients. Most patients who develop guttate psoriasis are children and teenagers. Guttate psoriasis is found to have a sudden onset following an acute streptococcal throat infection.
5) Erythrodermic Psoriasis
It is believed to be the least common type of psoriasis, yet it may be life-threatening. Erythrodermic psoriasis appears as a wide itchy, reddish, and peeling large area of the skin.
6) Psoriatic Arthritis
Which is a type of associated arthritis, is a common presentation in patients with psoriasis. 1 out of every 4 patients with psoriasis gets their joint affected. it is believed that psoriatic arthritis develops in 70% of patients after around 10 years of having psoriasis. Patients who develop psoriatic arthritis complain of pain, swelling, and stiffness in the joints and connective tissue, especially in the morning and upon getting up from a chair.
The joints of the hands, feet, lower back, neck, and knees are the most frequently affected joints. Undesired inflammatory reactions in these joints will lead eventually to movement restriction and reduction of the quality of life. The compromised physical activity resulting from psoriatic arthritis has significant negative psychological effects on the patients.
Distribution (Epidemiology)
Psoriasis is a fairly common disease affecting about 2-3% of the population worldwide. Psoriasis doesn’t have a certain geographical distribution; it affects all countries with different incidence rates. The prevalence of psoriasis is estimated to be 125 million patients all over the world. According to the United States census bureau, about 8 million patients with psoriasis are in the US. a cross-section statistical study conducted in the US revealed that white participants account for the most cases of psoriasis followed by Hispanic and African Americans. Asians record the lowest prevalence rate of psoriasis which is 0.5 % on average. Tracking the incidence trends for psoriasis among different countries is difficult due to insufficient and unavailable data.
Men, women, and kids are all equally at risk of developing psoriasis. Although it can manifest differently at any age, it often does at a young age between the ages of 10 and 30. The disease’s severity varies greatly from a little spot to massive patches occupying a wide area of the body, however, the mildest form of psoriasis which is easily controlled, accounts for 80% of cases.
Children may not necessarily inherit psoriasis to develop it because the disorder is multi-genetic, which means that different genes may each play a distinct role in contributing to certain disease traits. Moreover, the inherited genes don’t necessarily develop psoriasis by themselves, but it may increase its risk of occurrence if the patient is exposed to precipitating factors. Psoriasis can also run in families as statistical studies revealed that 3 out of 20 children may acquire psoriasis if one parent has it. If both parents have psoriasis, the offspring’s risk to develop psoriasis will be raised to 75%.
What Causes Psoriasis? What Triggers Psoriatic Lesions to Flare-up?
Although we don’t know for sure what causes psoriasis, our knowledge of its pathogenesis (how to work) is increasing. The most approved theory that explains the over-proliferation of the epidermal cells is the over-active immune response resulting from a triggering event. Dermatologists noticed some precipitating factors and events that usually precede the attacks of psoriasis. For some reason, these events trigger abnormal immune reactions.
These precipitating factors include:
1) Skin trauma is a common triggering factor for psoriasis. Psoriasis may be triggered by skin trauma or another disruption to the skin, contribute to the development of psoriasis or worsen pre-existing psoriasis. The integrity of both the epidermal and dermal layers of the skin must be disrupted by skin trauma or another injury. A wound, cut, laceration, gunshot wound, or skin abrasion are all considered different forms of skin trauma.
Skin trauma does not only mean physical injury but also chemical, thermal, and electrical injuries. Trauma may contribute to spreading psoriasis to healthy skin. The Koebner phenomenon, or the emergence of skin lesions of the same type of pre-existing disease, requires a substantial skin injury or other disruption to the epidermis to occur. Trauma-induced psoriatic lesions may take weeks to develop.
2) Some medications may cause or exacerbate psoriasis. Even though drug-induced aggravation may occur up to many months after the medication is initially administered, there is no way to find out whether this medication will induce psoriasis or not before taking it. Medication-induced psoriasis may persist or resolve spontaneously when the treatment is stopped.
Drugs may also cause brief exacerbations or flare-ups so make sure to inform your doctor about your medication. Drugs that may induce psoriasis include beta-blockers (hypertension medication), lithium, and ant-malarial drugs such as hydroxychloroquine. Although the topical steroid is used in the treatment of psoriasis, sudden withdrawal of steroids may induce an attack.
3) Stress and anxiety don’t induce psoriasis, but they worsen the condition of the psoriatic patients. Depressive disorders may contribute to an exacerbation of psoriasis and induction of acute attacks. In case of the presence of a psychological disorder, it should be treated simultaneously with psoriasis.
4) Sore throat caused by streptococcal infection may trigger the development and aggravation of guttate psoriasis. Streptococcal infections of other parts other than the throat aren’t reported to induce psoriasis. Guttate psoriasis may resolve spontaneously within weeks after treatment of the sore throat.
5) Decreased exposure to sunlight is believed to increase the susceptibility to developing psoriasis. Frequent exposure to sunlight maintains the vitality of the skin and keeps it healthy. Ultraviolet rays of the sun reduce the severity of psoriasis by slowing down the proliferation (growth) rate of the epidermal cells.
Diagnosis and Investigation
The diagnosis of psoriasis is made clinically based on the experience of the dermatologist. Skin biopsy is not frequently used to diagnose psoriasis as the typical presentation of psoriasis Vulgaris (plaque psoriasis) is usually easily diagnosed and doesn’t require further investigations. Dermatologists may use characteristic clinical signs of psoriasis as Auspitz sign which involves manual removal of the white scales of psoriasis that will lead to an eruption of small bleeding spots.
The dermatologist may ask about a family history of psoriasis to include or exclude genetic involvement. Rarely, dermatologists may ask you to do lab tests or blood work to rule out other suspected diseases.
Complications and Psychological Impact
Although many patients may think that psoriasis affects only the skin, it may affect internal organs if it isn’t adequately treated. Complications of psoriasis are less common nowadays due to better treatment options. These complications are:
1) Type 2 Diabetes Mellitus is found to have a higher incidence rate for patients with psoriasis. Although doctors aren’t clear about the correlation between diabetes and psoriasis, it is believed that each disease is a risk factor for the other. Psoriasis also worsens the condition of diabetes in the previously diagnosed diabetic patients.
2) Irreversible Joint Damage resulting from psoriatic arthritis is one of the most undesired complications of psoriasis. The inflammatory reactions accompanying psoriatic arthritis may result in severe damage and destruction of the joint. impairment of joint articulation could be reversible if it is treated early enough, otherwise, the patient will experience a significant reduction in joint mobility.
3) Eye Issues are more frequently seen among psoriatic patients as they are at higher risk of developing conjunctivitis, uveitis, scleritis, and cataracts. The exact correlation between psoriasis and eye problems is arguable and still under research. It is believed that two-thirds of psoriatic patients will develop some sort of eye condition. For instance, up to 20% of patients with psoriasis have uveitis.
4) Parkinson’s Disease is a reported complication of psoriasis. Parkinson’s disease is a neurological disease affecting mainly the motor system and causes static tremors. There is no concrete explanation of what links psoriasis with a neurological disease, yet psoriatic patients are at more risk of developing Parkinson’s disease.
5) The Psychological Impact of chronic illnesses such as psoriasis is unneglectable. Dealing daily with the stress of having an incurable disease could be overwhelming for many patients. Although the available treatment significantly alleviates the symptoms of psoriasis and reduces the risk of complications, it is still hard to cope with the emotional aspects of the disease. A statistical study conducted in 2016 showed that approximately 16.5% of psoriatic patients are at some level of major depressive disorder. Unfortunately, anxiety and stress worsen the condition of psoriasis and may trigger a flare-up.
6) Lymphoma is a tumor of the lymphatic system. Patients with moderate to severe psoriasis are more susceptible to developing cancer, especially lymphomas. Some research papers state that the risk of developing lymphoma is 1.3 to 2 times more in psoriatic patients than in the general population.
7) Secondary Bacterial Infection is a probable complication of most skin lesions especially if treated with immunosuppressants such as psoriasis.
Treatment of Psoriasis
There isn’t an ultimate cure for psoriasis, but there are different types of therapies that significantly reduce the symptoms of psoriasis. No matter where it is or what type it is, psoriasis is frequently worse by touch, especially by wearing tight clothing like underwear with elastic waistbands and socks.
If your psoriasis is prone to flare up or while you’re receiving treatment, it may be helpful to wear looser clothing in certain areas. Not to mention the necessity of avoiding the precipitating factors that may trigger a flare-up. Besides a proper treatment plan, following a healthy lifestyle free of stress, smoking and alcohol would help significantly relieve psoriasis. Psychological support is often an overlooked and ignored side of the treatment, however, it has a great impact.
According to the patient’s symptoms, his dermatologist will choose the proper treatment plan. The treatment plan for psoriasis will consist of one or more of the following:
1) Topicals
Topicals are the most used line of treatment for mild to moderate psoriasis. Topical steroid is the medication of choice, especially for plaque psoriasis. Steroids are potent anti-inflammatories that reduce the symptoms of inflammation that accompany psoriases such as redness and itching. Topical salicylic acid is used as a keratolytic which exfoliates the upper layers of the skin and removes excessive scales.
Many dermatologists may also prescribe calcipotriol (a synthetic form of vitamin D) because it is believed that vit. D deficiency may exacerbate psoriasis. Moreover, the combination of steroids with calcipotriol is found to reduce remarkably skin irritation. Your doctor may ask to apply a scale softener to avoid over-dryness of the skin. Topical coal tar is used to treat psoriasis, particularly the plaque type for a long time and proved its effectiveness meanwhile, however, we don’t know much about it, so it is not recommended for pregnant and breastfeeding women.
2) Phototherapy
It is a well-known method of treatment of psoriasis that mainly involves scheduled skin exposure to ultraviolet rays. Ultraviolet rays are emitted naturally from the sun, yet dermatologists don’t usually recommend over-exposure to direct sunlight to avoid sunburns. Phototherapy which is also called light therapy is believed to reduce the size of the psoriatic patches and decrease the rate of growth of the skin cells. Ultraviolet radiations have three primary types; A, B, and C. The ultraviolet rays that are used in the treatment of psoriasis are UVA and UVB.
Patients could obtain UVB from special lamps or excimer lasers. The dermatologist will choose whether the psoriatic patient needs a broad-band or narrow-band UVB exposure according to the severity of psoriasis and the tolerability of the patient. UVA is not effective in the treatment of psoriasis unless a light-sensitizing agent is applied/taken orally before it in an approach called PUVA (psoralen + UVA). Phototherapy is less recommended in severe psoriasis occupying wide skin areas due to the higher risk of radiation side effects.
3) Systemic medications
Systemic medications are less common in the treatment of psoriasis. Oral drugs expose the patients to more adverse effects than topical medications, so dermatologists usually don’t consider them the first choice of treatment unless there is a severe form of psoriasis. Most oral drugs used in controlling psoriasis act by suppressing the immune system which is accused of developing psoriasis.
Methotrexate and cyclosporine are the most common immune suppressants used to treat psoriasis. Since 2003, biological agents that act by inhibiting chemical mediators of the inflammatory reactions are used in the treatment of psoriasis. In April 2004, etanercept is approved by the FDA (Food and drug administration) for the treatment of psoriasis.
Prognosis
Psoriasis is a chronic inflammatory disease that has no cure till now, yet it is very controllable. The early-treated cases of psoriasis usually don’t face any reduction in the quality of life. Psoriasis’s typical course consists of attacks of exacerbation (flare-ups) followed by periods of remission that vary in length. There is no valid data about patients who had their psoriasis cured on its own.