Psoriasis: Clinic, diagnosis and treatment

Medical editor: Dr. Pierre Schneider, Dermatologist, Saint-Louis Hospital, France.

Written by

Dr. Pierre Schneider

Key messages:

Psoriasis is a chronic itchy skin condition, with a complex physiopathology involving genetic and environmental factors.
Bastion areas are: elbows, knees, scalp and back.
Plaque psoriasis (psoriasis vulgaris) represents about 90% of all cases. It is characterized by thick red plaques covered in white scales.
Other areas may be affected (less common): skin folds, genitals or nails.
Untreated psoriasis can lead to skin infection or psoriatic arthritis.
More importantly, it can have profound repercussions on patients ‘quality of life: depression, anxiety and social stigma.
Treatment depends on the extent and severity of the lesions and ranges from dermocorticoïds or topical corticosteroids, to the use of biotherapies (hospital settings) or the hospitalization of patients in special units for severe cases.

Psoriasis is a chronic skin condition characterized by red, scaly rashes that may be itchy or painful.
The skin patches can develop anywhere on the body, but are most often located on the elbows, knees, scalp and back, referred to as bastion areas.
The exact cause of psoriasis is unknown, but it is thought to be related to an overactive immune system that causes an abnormal acceleration of the skin cell renewal cycle.
Psoriasis is a common disease that affects about 2-4% of the world's population. It can affect people of any age².

The physiopathology of psoriasis is complex and not fully understood. However, it is generally considered to be caused by an abnormal response of the immune system to unknown stimuli. This leads to an increase in the production of skin cells called keratinocytes, which accumulate in thick layers on the skin surface².
Studies have shown that cytokines, TNF-alpha and interleukin-17 (IL-17) in particular, play an important role in the physiopathology of psoriasis. These molecules, produced by immune cells, can stimulate the production of keratinocytes and cause inflammation².
Psoriasis can also be influenced by environmental factors such as stress, infection, skin injury/trauma, climate and certain medications. A family history of psoriasis may also increase the risk of developing the disease².

In conclusion:

The physiopathology of psoriasis is complex and involves an intricate interplay between genetic and environmental factors as well as abnormal immune system responses.
In recent years, numerous advances were made in the understanding of the physiopathology of this disease, which have led to the development of new highly effective treatments for this condition².

It is very important for health professionals to recognize and understand the various clinical forms of psoriasis so that they can prescribe a relevant treatment and a comprehensive care package².

Common clinical forms of psoriasis

Plaque psoriasis (psoriasis vulgaris)

It is the most common form of psoriasis, representing about 90% of cases.
It is characterized by thick red plaques covered in white scales.
The plaques generally develop on elbows, knees, back and scalp.

Guttate psoriasis

This form of psoriasis is characterized by small red scaly spots, often caused by an infection of streptococcal bacteria.
This form can appear suddenly and can affect children and young adults.

Pustular psoriasis

This form is characterized by pustules full of liquid on reddened skin.
The pustules can spread to wide areas of the body or be limited to specific zones, especially the palms of the hands and the soles of the feet.

Erythrodermic psoriasis

It is a rare and serious form of psoriasis, characterized with generally reddened skin (more than 90% of the skin surface is affected) and scaling.
This form can trigger severe complications and requires urgent medical attention.

Fig: Erythrodermic phenotype psoriasis

Psoriasis targeting a particular area of the body

Psoriasis can damage the skin in specific areas:

The scalp

Psoriasis on the scalp can trigger itchiness and dandruffs.
Treatments include topical medication and specialist shampoos.
In case of resistance to the treatment, systemic treatments or biotherapy can be considered.

Fig: Psoriasis on the scalp

Skin folds or reverse psoriasis

Skin folds, such as armpits, elbows and knees can be affected by psoriasis, triggering pain and discomfort when moving.
Treatments include topical medication and systemic treatments, or biotherapy.

Genitals

Psoriasis can affect the genitals, triggering painful and itchy sensations¹.

Nails

Psoriasis can affect the nails, triggering changes in the nail structure, with splits, ridges, thickening or painful detachment, as well as social anxiety.
This form of psoriasis represents a higher risk of developing into psoriatic arthritis.

Fig: Nail psoriasis

Assessing the severity of psoriasis

There are several ways of assessing the severity of psoriasis:

The Psoriasis Area and Severity Index (PASI)

This scale measures the severity of psoriasis by assessing the surface area and severity of skin plaques, as well as inflammation and scaling⁴.

Nail Psoriasis Severity Index (NAPSI)

This scale measures the severity of nail damage by psoriasis³.

The Dermatology Life Quality Index (DLQI)

This scale measures the impact of psoriasis on the patients’ quality of life⁵.

Psoriasis is a chronic disease, which can trigger complications when not treated properly. Health professionals must be aware of the possible complications triggered by psoriasis to ensure that they provide patients with a comprehensive treatment².

Skin complications

Skin lesions from psoriasis can become infected, triggering pain and other symptoms.
Psoriasis plaques can also be painful and distressing, impacting on the patients’ ability to perform daily living tasks.

Joints complications

Psoriasis can also trigger joints disorders, which can trigger pain and inflammation of the joints.
This is known as psoriatic arthritis¹.

Psychological complications

Patients with psoriasis can have their quality of life profoundly affected and may suffer from depression, anxiety and social stigma because of their physical appearance.
Health care professionals need to be aware of these psychological effects and work with patients to manage them.

Metabolic complications

Psoriasis can trigger metabolic complications such as diabetes, heart diseases and disorders of lipid metabolism.

Side effects

Treatments used to treat psoriasis can cause unwanted side effects, such as skin dryness, irritation and photosensitivity.
Healthcare professionals should work with patients to minimize these side effects and ensure optimal management.

Eczema

It can be difficult to distinguish eczema from psoriasis because of skin similarities such as red patches and itching.
However, eczema may be associated with intense skin dryness while psoriasis is often associated with severe scaling¹.

Pityriasis rubra pilaris

This skin disease is characterized by thick, itchy patches similar to psoriasis¹.

Seborrheic dermatitis

This skin disease is characterized by red patches and oily scales and can be confused with psoriasis.
However, seborrheic dermatitis is often associated with increased sebum production, whereas psoriasis is not¹.

Lichen planus

This skin disorder is characterized by thick, flat lesions that can be mistaken for psoriasis.
However, lichen planus does not usually occur on the elbows and knees, which are areas frequently affected by psoriasis¹.

Fig 1,2: Lichen planus

There are several treatments available for patients with psoriasis, ranging from topical treatments such as topical creams and ointments, to systemic treatments such as oral medications and biological therapies².

Localized plaque psoriasis

Topical treatment

Use of salicylic acid preparations for hyperkeratotic forms to remove scales, which then allows for a more effective dermocorticoids follow-up treatment.
Application of topical corticosteroids:
- Level 1 on the corticosteroid therapy ladder: corticosteroids in the form of gel, foam, cream, shampoo. Suitable for the treatment of scalp psoriasis.
- Level 2 non-fluorinated topical corticosteroid therapy in the type of hydrocortisone 17-butyrate: treatment of reverse psoriasis and genital psoriasis.
Vitamin D analogues:
- Calcipotriol is the most effective but not as potent as a level 2 corticosteroid. Previously used on its own, it is now used in combination with a corticosteroid in the same tube of ointment or gel. It is suitable for the treatment of limited plaque psoriasis.
- Daily application until the lesions are whitened, on average six weeks for plaque psoriasis and three weeks for damage to the folds, followed by a reduced application every other day, then twice a week as a maintenance treatment.

Psoriasis in widespread plaques

Treatments usually prescribed by dermatologists

Phototherapy:
- PUVA therapy: combination of psoralen (meladinine) and UVA irradiation in progressive doses. Cures of twenty sessions at a rate of three per week. Disadvantages: intolerance to meladinine (digestive problems). Increased risk of skin cancers due to the accumulation of U.V. doses received, especially when the patient increases the doses through exposure to natural sunlight (heliotherapy).
- Narrow-band UVB phototherapy (TL01): gradually replaces PUVA therapy, no need to take meladinine, lower risk of skin cancer. Can be used on children and pregnant women.
Retinoids: use in progressive dosage. Efficacy is limited by the side effect of embrittlement of the skin and its appendages: lip damage and dry eyes that may contraindicate the use of contact lenses. Biological monitoring is simple (hepatic and lipidic), but treatment of women of childbearing age requires effective contraception, which must be prolonged for two years after the end of the treatment. It is the treatment of choice for psoriasis in children.
Methotrexate: reference treatment for severe psoriasis and/or psoriasis associated with joint problems. Prescribed as an injectable or tablet. The therapeutic strategy is well structured: pre-therapeutic assessment, implementation and follow-up. The main limitation is liver toxicity. Contraception is imperative in fertile women during treatment and three months after its cessation. The same duration of contraception is recommended for men.

Treatments implemented in a specialized hospital setting

Cyclosporine: renal and hypertension monitoring.
Biotherapies: historically, TNF-Alpha inhibitors were used, but new molecules are appearing on the market. They are indicated after failure of a systemic treatment (phototherapy, methotrexate) or contraindications to these in the case of severe psoriasis. They require a pre-therapeutic assessment in a day hospital including the screening for infectious areas, particularly latent tuberculosis. This treatment also allows the correction of comorbidities by taking into account the notion of metabolic syndrome (obesity, hypertension, diabetes) closely associated with psoriasis.

Severe cases of psoriasis (generalized pustular psoriasis, also known as Erythrodermic psoriasis)

These cases require hospitalization and care by specialized teams.

Accompanying dermo-cosmetic products

Body

Gentle daily hygiene associated with the daily application of an emollient on the plaques, which must be used in association with a topical or general medical treatment. This routine should be continued once these treatments are completed, even after the reduction or the disappearance of lesions.
Avoid microtrauma as much as possible since it can induce or worsen psoriasis lesions.
Rubbing, scratching or picking at scales can particularly reactivate psoriasis for several days.
The fight against itching is one of the fundamental elements in the prevention of recurrences.

Scalp

Use a shampoo-cream for scaly scalps, alone or in combination with a medicated treatment, alternating with a mild shampoo.
The shampoo-cream is to be used 3 times a week during the 3-week flare-up period, then once to twice a week for maintenance.
It is advised to use 2 applications, leaving the product on for 5 minutes during the second application.

Generalized pustular psoriasis: what are the risks for pregnant women? Are they any effects on the baby?

The risks, for both mother and baby, are linked to the severity of the symptoms and the treatments that may be used for ailments other than the psoriasis itself. These forms of psoriasis are obviously treated in a specialized environment to manage these different factors.

What measures can be taken to prevent a flare-up?

In order to prevent flare-ups, use an emollient and remove stress and causes of fatigue.

Is there a recurring effect from pregnancy or postpartum?

The impact of pregnancy on psoriasis varies from patient to patient. Postpartum recurrence is frequent, triggered by fatigue and short nights.

Should swimming pools be avoided?

There is no contraindication to swimming; it is neither harmful nor beneficial.

Should a pregnant woman who was affected with psoriasis in the early stages of pregnancy be referred to a dermatologist? Should her treatment be adapted to prevent the lesions from getting worse during pregnancy?

A systematic consultation with a dermatologist should not be recommended when a pregnant woman has a history of psoriasis. She will only need to see a dermatologist if a flare-up that does not respond to her usual treatment. In case of systemic treatment, pregnancy is contraindicated, and contraception is mandatory for women of childbearing age.

Psoriasis: Clinic, diagnosis and treatment

Digest

Definition

Etiology and physiopathology

Clinic

Complications

Differential diagnosis

Treatments

Questions your patients may have

References