Psoriasis – Causes, Symptoms, Diagnosis and Treatment

Psoriasis is a common, chronic inflammatory disorder present all over the world, involving about 2% of the population. It affects both sexes and presents at any age though it is most common in the second and third decades of life.

Aetiology

Psoriasis is considered to be an autoimmune disorder with a strong genetic predilection. Certain HLA markers are recognized. HLA-CW6 is implicated in it and HLA-B13, HLA-B16 and HLA B27 in psoriatic arthropathy.

Commonly there is a family history of it though it may skip & generation and in some families, a child may develop the disease before the parents. When one parent has it, 8% of off springs develop it while when both parents have the disease, incidence in off springs shall be 41%. Some individuals may never develop it despite carrying the genetic predilection.

Some factors may act as trigger mechanism for it. Physical trauma is a major factor in eliciting lesions. Rubbing and scratching stimulates the proliferation of disease process. Stress is another important factor.

It may be mental stress, endocrinal imbalance and physiological changes of puberty and pregnancy. Infections like exotoxins from bacterial (streptococcal) and fungal play part in precipitating psoriasis.

Drugs like Lithium, B-blockers, Ant malarial, NSAID’s etc are known to induce it by inhibiting adenylcyclose activity. This in turn alters epidermal cell kinetics.

Psoriasis

Pathogenesis

It includes:

1. Epidermal cell proliferation, with shortening of epidermal cell cycle time. There is marked thickening and also thinning of the epidermis with elongation of rete edges, increased proliferation of keratinocytes, fibroblasts and endothelial cells.

2. T cell infiltration of the skin along with inflammatory cells in the epidermis and dermis forming micro abscesses in the stratum corneum.

3. Alteration in the cell kinetics of keratinocytes.

4. Polyamines play important role in regulating cellular proliferation. This is regulated by phospholipase and arachidonic acid via lipoxygenese pathway.

5. Humoral and cellular abnormalities in the form of elevated IgA levels and alteration of T cell function. Maintenance of psoriatic lesions are an ongoing auto immune response.

Clinical features

Psoriasis presents in many forms. Classically the lesions are well-demarcated, erythematous, scaly plaques, salmon pink in color present at various sites (trunk, arms, nails and scalp). The scales are loosely adherent and when these are scraped tiny bleeding spots are seen (Asupitz sign). Lesions are usually asymptomatic. Pruritis is of present in 15-20% of cases of psoriasis.

To start with lesions of it are variable in size in the form of a papule. Coalescence of these results in the formation of plaques of various sizes and shapes. These are primarily present on the trunk and limbs though all parts of the body may be affected.

Involvement of scalp may be localized or wide spread. Thickened hyper keratotic scales are common. Psoriasis in scalp has tendency to extend to forehead. There may be mild to severe pruritis which often causes subconscious scratching.

Psoriasis of scalp is part of generalized disease. It does not lead to hair loss. Nail involvement is in the form of pitting of the nail plate, separation of the distal end of nail bed by subungual hyperkeratotic material. Toe nails are more commonly affected.

There may be history of trauma to the toe. New lesions of psoriasis appear at the sites of trauma. (koebner or isomorphic phenomenon). Infection, injury and sunlight worsen the disease. Healing results in lesions becoming non-scaly and dusky assuming annular form.

Varieties of Psoriasis

Psoriasis vulgaris (Plaque Psoriasis)

It is the most common variety, characterized by plaques of varying sizes present on the elbow, knees, trunk and scalp. Nail involvement is equally common.

Flexural psoriasis

It is uncommon form of it where plaques may or may not be seen. It is also labeled ‘inverse psoriasis’. Lesions are shiny smooth pinkish with absent scales, principally present in groin, perianal and genital regions.

Guttate Psoriasis

It is commonly seen in children and young adults. A child will develop a sore throat a week before the appearance of sudden crops of small erythematous, slightly raised eruption over the trunk and upper extremities. Scales are usually absent in this variety of it. In half of the cases the disease resolves spontaneously while in others, it may later become reactivated as chronic plaque form.

Pustular psoriasis

Here small pustules appear on the psoriatic or normal skin. Pustular psoriasis is further divided into (i) Palmo plantar where the palms and soles are primarily involved (ii) Generalized pustular type. Here there is generalized involvement of the body. Constitutional symptoms in the form of fever, malaise, arthralgia are present. The pustules may rupture leaving behind denuded areas.

Erythrodermic psoriasis (Exfoliative psoriasis)

There is a sudden flare up of the disease when the whole body becomes inflamed. There is itching and burning sensation. Generalized exfoliation occurs. Constitutional symptoms are severe. Thermo regulatory functions may be deranged and disease may even prove fatal.

Nail involvement

It may be present in isolation, not more than 25-50%, cases of it get involvement of nails. Most common changes include pitting of nails, separation of nail plate from nail bed, formation of vertical ridges, deep transverse grooves (Beau’s lines) and nail discoloration (Red Brown, salmon pink or oil stain coloration) Hyperkeratosis of the nail is typical pattern.

Psoriatic arthropathy

It may be in the form of a single or few, small joints involvement especially distal inter phalange joints. It is a mild and chronic condition. Nail involvement is commonly seen. Severe destructive form of arthritis may occur in some though it is seronegative. Uncommonly spine may be involved producing picture like Ankylosing spondylitis.

Differential diagnosis

Typical case of psoriasis is easily diagnosed with the presence of plaques, silvery scales and presence of bleeding spots on removing the scales. Differentiation has to be made from seborrhoeic dermatitis, pityriasis rosea and psoriasiform lupus vulgaris.

Course of the disease

It is a chronic disease, which remains for many years with periods of remission. Disease is often exacerbated by emotional stress, trauma, intercurrent infections, cold months, during pregnancy, puberty and menopause.

Treatment

Before embarking on specific treatment due consideration should be given to the patients psychological aspects. Most of the patients are under stress because of the disease and are often depressed. This aspect of the patient be given due consideration. Treatment primarily shall consist of topical and systemic therapy.

Topical treatment Localized lesions are treated with any of the therapy ranging from coal tar, Dithranol, Topical steroids, emollients and vitamin D analogues. A great percentage of patients with mild to moderate disease are managed by topical therapy.

An ideal drug for local treatment of psoriasis is one which inhibits the immune response, decreases keratinocyte proliferation and increases maturation of the cells.

Coal tar

It has got anti-mitotic effects. Crude coal tar bath (2.5%) followed by ultraviolet light exposure shows improvement in 70-80% of patients in 4-6 weeks- Draw backs of coal tar therapy are that it is messy and can stain clothes as well as cause allergic reaction. Moreover it has carcinogen potential.

Dithranol

It is a synthetic derivative of Chrysarobin. It is an effective treatment and produces clearance of psoriatic lesions in 3 weeks. Ingram Regime consists of a tar bath, followed by UVB exposure and covering psoriatic lesions with Dithranol paste (0.05 to 0.5%) for 18-20 hours with bandages. It is irritant to skin and may cause bums. It is not suitable for application on head and neck.

When lesions clear, they leave behind unsightly hyper pigmented lesions. Untoward reactions to Dithranol can be avoided by using it for short periods ranging from 10 minutes to 30 minutes and progressively going to 2 hrs.

Topical steroids

For localized psoriasis, steroids (Clobetasol Propionate 0.05% alone or in combination with salicylic acid) are effective in bringing the disease under control. In cases of long standing, intradermal injection of triamcinolone alone thrice weekly helps to resolve the condition.

Often ointment form of steroids is applied followed by thin plastic material. Side effects of topical steroids includes thinning of the skin, striae, telangiectasia and tachyplaxis. Long term use of steroids shall lead to other systemic effects like disturbances of glucose metabolism, cushings like syndrome and flare up of bacterial infections.

Vitamin I analogues

They act by decreasing cell proliferation, increase keratinocyte maturation and have immuno modulatory effect by inhibiting the cytokine production of keratinocytes and lymphocytes.

Absorption of these analogues from skin causes hypercalcaemia. Important members of this group are Calcipotriol and Tacalcitol. Because of the side effects associated with their use total dose of Calcipotriol should not exceed 100 G/week and of tacalcitol to 30 G/Week. These drugs are indicated in chronic plaque type of psoriasis. Because of their irritation effect they should not be applied on face.

Photo chemotherapy (Puva)

In this form of therapy, Psoraleln (0.6 mg/kg body weight) is administered two hours before exposure to UVA light. It is given two to three times a week for 2-15 minutes for 10-12 weeks.

This form of therapy is indicated in severe form of it or those who are not responding to other therapies. The mode of action is anti-proliferative effect .of light on rapidly multiplying keratnocytes. PUVA therapy is contraindicated in patients of hepatic, renal or cardiovascular diseases. Long term risks of skin cancer are also there.

Systemic therapy

It includes corticosteroids, methotrexate, Vit A analogues and cyclosporina.

Methotrexate: A weekly dose of methotrexate (7.5-15 mg) is indicated in severe cases of psoriasis. Response to drug is observed after 3-4 weeks and clearance may be observed after 8-12 weeks. After this the patient is maintained on a weekly dose of 5- 10 mg for 2 years. Patients on this drug must be monitored for liver damage.

Corticosteroids

Systemic use of corticosteroids is not indicated except in exfoliative dermatitis form of it and psoriasis arthropathy. Triamcinolone is the most effective corticosteroid in psoriasis but it induces myopathy. Sudden stoppage of steroids must not be done since it shall induce severe relapse.

Vitamin A analogues

These are useful for the treatment of complicated and chronic resistant plaque type of psoriasis. They are also employed in pustular and arthropathic variety of the disease. Commonly used is second generation retinoid (Etretinate) in a dose of 0.2-1 mg/kg per day. Side-effects include dryness of the skin, stomatitis, chapped lips and epistaxis.

The drug is effective since it normalizes keratinocyte growth, but it is highly teratogenic and is not to be used in women of child bearing age.

Regular monitoring of liver and lipid profile should be done.

Cyclosporin-A

It acts as an immuno suppressant by blocking an early stage in the activation of cytotoxic T lymphocytes after the recipient is exposed to the antigen. Dose is 3-5 mg/. kg per day orally. It is almost completely metabolized. It achieves partial clearance of lesions and gives patient quality of life. Topical therapy in addition is indicated. Side-effects include nephrotoxicity, gums hypertrophy hepatotoxicity, increased susceptibility to infections and development of lymphomas.

Treatment of regional psoriasis

Psoriasis vulgaris

1. Patients with few plaques (2-3) use of mild emollients or mild keratolytics (2% salicylic acid ointment) is sufficient.

2. For moderate involvement, topical steroids (0.1% Betamethasone valerate / propionate) is applied twice a day. Prolonged use leads to decrease in potency. Skin atrophy and telengactesia develops.

3. Vit D analogue (Calciprotriene 0.05%) is a good non-steroidal alternative. Topical retinoids is another alternative.

4. When there is extensive involvement, topical treatment with PUVA therapy is to be combined with methotrexate / cyclosporin.

Psoriasis Vulgaris (Guttate Type)

1. Antibiotics (Penicillin I Erythromycin) to combat streptococcal infection

2. PUVA therapy.

Psoriasis Vulgaris (Scalp)

1. For mild superficial scales, Tar or Ketoconazole shampoo followed by topical corticosteroids.

2. For thick scales, a keratolytic gel is used (2- 10%, salicylic acid ointment in mineral oil) over the scalp, covered with an occlusive plastic cap and left overnight. When scales are loosened, a steroid lotion or Calcipotriol ointment is applied on scalp.

3. Intralesional corticosteroids may be used for isolated plaques.

Nail psoriasis

1. Nail psoriasis is difficult to treat. Relapses are common. Often improvement of nail psoriasis occurs along with remission of cutaneous lesions.

2. Removal of subungal debris and application of steroids under occlusion offers some relief. Intra dermal injection of Triamcinolone into the nail bed may be beneficial.

3. PUVA photo chemothera3y is also effective.

4. Systemic retinoids, methotrexate and calcipotriol can be used in resistant cases.

5. 40% urea ointment is helpful in the removal of hypertrophic and dystrophic nails. Subsequent use of topical therapy may restore normal nails.

Psoriasis (Palms & soles)

1. Combination of oral retinoids and PUVA photochemotherapy is beneficial.

2. In severe cases methotrexate.

Psoriasis of perianal and genital regions

1. Strong topical ointments shall cause irritation.

2. Vit D analogue (Calciprotriene’) ointment is effective and gives relief.

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