Psoriasis is a chronic skin disorder characterized by excessive proliferation of keratinocytes, resulting in the formation of thickened scaly plaques, itching, and inflammatory changes of the epidermis and dermis. The various forms of psoriasis include guttate, pustular, and arthritis variants.
SIGNS AND SYMPTOMS OF PSORIASIS
• Approximately 85% of patients with psoriasis have mild-to-moderate disease.
• The primary psoriatic lesion is an erythematous papule topped by a loosely adherent scale. Scraping the scale results in several bleeding points (Auspitz sign).
• Chronic plaque psoriasis generally manifests with symmetric, sharply demarcated, erythematous, silver-scaled patches affecting primarily the intergluteal folds, elbows, scalp, fingernails, toenails, and knees. This form accounts for 80% of psoriasis cases. Psoriasis may also involve the forehead, particularly contiguous to the scalp.
• Psoriasis can also develop at the site of any physical trauma (sunburn, scratching). This is known as Koebner’s phenomenon.
• Nail involvement is common (pitting of the nail plate), resulting in hyperkeratosis, onychodystrophy with onycholysis.
• Pruritus is variable; soreness and bleeding may occur.
• Joint involvement can result in sacroiliitis and spondylitis.
• Guttate psoriasis is generally preceded by streptococcal pharyngitis and manifests with multiple droplike lesions on the extremities and the trunk.
• Adverse effect on psychological and social functioning, with affected persons often feeling stigmatized.
CAUSES OF PSORIASIS
• Unknown, but there is a strong genetic component and high heritability. There are at least nine chromosomal loci with linkage to psoriasis. These loci are called psoriasis susceptibility 1 through 9 (PSORS1-PSORS9). PSORS1 locus in the major histocompatibility complex (MHC) region on chromosome 6 is considered the most important susceptibility locus and is believed to account for 35% to 50% of the heritability of the disease.
• Familial clustering (genetic transmission with a dominant mode with variable penetrants).
• One third of persons affected have a positive family history.
• A high prevalence of celiac disease has been noted in patients with psoriasis.
DIAGNOSIS OF PSORIASIS
DIFFERENTIAL DIAGNOSIS OF PSORIASIS
• Contact dermatitis.
• Atopic dermatitis.
• Stasis dermatitis.
• Nummular dermatitis.
• Mycosis fungoides.
• Cutaneous systemic lupus erythematosus.
• Secondary and tertiary syphilis.
• Drug eruption.
• Dermatomyositis (DM).
• Lupus erythematosus (LE).
• Seborrheic dermatitis.
• Pityriasis rosea.
• Lichen planus.
• Diagnosis is clinical. Blood work is rarely needed.
• Skin biopsy is rarely necessary.
LABORATORY TESTS OF PSORIASIS
Generally not necessary for diagnosis.
TREATMENT OF PSORIASIS
• Sunbathing generally leads to improvement.
• Eliminate triggering factors (e.g., stress, certain medications [e.g., lithium, beta blockers, antimalarials]). Severe emotional stress tends to aggravate psoriasis.
• Patients with psoriasis benefit from a daily bath in warm water followed by application of a cream or ointment moisturizer. Regular use of an emollient moisturizer limits evaporation of water from the skin and allows the stratum corneum to rehydrate itself.
• PUVA therapy.
• Local hyperthermia has been used successfully to clear psoriatic plaques, but relapse is common.
• Occlusive treatment with surgical tape or dressings is effective as monotherapy or in combination with topical medications.
GENERAL Rx OF PSORIASIS
Therapeutic options vary according to the extent of disease. Approximately 70% to 80% of all patients can be treated adequately with topical therapy.
• Patients with limited disease (<20% of the body) can be treated with the following:
1. Topical steroids: disadvantages are brief remissions, expense, and decreased effect with continued use. Salicylic acid can be compounded by pharmacist in concentrations of 2% to 10% and used in combination with a corticosteroid to decrease the amount of scale.
2. Calcipotriene: a vitamin D analogue effective for moderate plaque psoriasis. Adults should comb the hair, apply solution to the lesions, and rub it in, avoiding uninvolved skin. Disadvantages include its cost and potential burning and skin irritation. It should not be used concurrently with salicylic acid because calcipotriene is inactivated by the acidic nature of salicylic acid. Taclonex ointment and enstilar aerosol foam formulation are a combination of calcipotriene and the high-potency corticosteroid betamethasone dipropionate. They are well tolerated and more effective than either agent used alone but also much more expensive.
3. Tar products (Estar, LCD, Psorigel) can be used overnight and are most effective when combined with ultraviolet B (UVB) light (Goeckerman regimen).
4. Anthralin: useful for chronic plaques; can result in purple-brown staining; best used with UVB light.
5. Retinoids such as tazarotene 0.05%, 0.1% cream or gel, are effective in thinning plaques but are expensive and can cause irritation.
6. Other useful measures include tape or occlusive dressing, UVB and lubricating agents, and interlesional steroids.
• Therapeutic options for persons with generalized disease (affecting >20% of the body) and for those with inadequate response to topical agents:
1. UVB light exposure three times a week: this therapy does not require administration of a systemic drug (unlike psoralen plus ultraviolet A [PUVA]), but to be effective, it requires removal of scale with keratolytic agents and emollients.
2. Oral PUVA administered two to three times weekly is effective for the generalized disease. It is often considered in patients for whom narrow-band UVB therapy is ineffective. However, many PUVA treatments are required, necessitating frequent office visits, and it may be associated with phototoxicity, such as erythema and blistering, and an increased risk of skin cancer.
• Systemic treatments include methotrexate 25 mg/wk for severe psoriasis. Etretinate (a synthetic retinoid) is most effective for palmar-plantar pustular psoriasis. Dose is 0.5 to 1 mg/kg/day. It can cause liver enzyme and lipid abnormalities and is teratogenic.
• Apremilast is a phosphodiesterase type-4 inhibitor used in moderate to severe plaque psoriasis. Side effects include diarrhoea, nausea, headache, and worsening depression.
• Cyclosporine is also effective in severe psoriasis; however, relapses are common.
• Chronic plaque psoriasis may be treated with alefacept, a recombinant protein that selectively targets T lymphocytes. Treatment with alefacept for 12 wk (0.025, 0.075, or 0.150 mg/kg of body weight IV weekly) may result in significant improvement. Some patients also demonstrate a sustained clinical response after the cessation of treatment. This medication is very expensive (a 12-wk course can cost >$8000).
• TNF inhibitors (adalimumab [Humira], etanercept [Enbrel], infliximab [Remicade]): Trials revealed a reduction in severity of plaque psoriasis. Efalizumab, a humanized monoclonal antibody that inhibits the activation of T cells, has also been reported to produce significant improvement in plaque psoriasis treatment period. Adalimumab has been reported to be effective for joint and skin manifestations of psoriasis.
• Newer biologic agents in patients with moderate to severe plaque psoriasis are ustekinumab (Stelera; an interleukin-12 and interleukin-23 blocker), brodalumab (Siliq), ixekizumab (Talz), secukinumab (Cosentix) anti–interleukin-17 receptor antagonists, and guselkumab (Tremfya), an interleukin-23 blocker. Cost is a limiting factor with all these agents.