SCALP PSORIASIS

SCALP PSORIASIS AND ITS MANAGEMENT

DEFINITION:

The scalp is a well know predilection site for psoriasis. Scalp psoriasis is characterised by widespread or focal, scaly,erythematous , hyperkeratotic plaques often involving the occiput and the retroauricular skin.

CLINICAL FEATURES:
The scalp is a favoured site for psoriasis and may be the only site affected. More than 50% of psoriasis population is affected with scalp psoriasis. The plaques of scalp psoriasis similar to those of the skin except that the scalp is more readily retained, and also by the fact that the lesions on the scalp are frequently assymetrical. Picking, scratching, and harsh shampooing which leads to koebnerisation, may be responsible for the assymetrical distribution.

Scaling and itching are the two main complaints in scalp psoriasis. In general, psoriasis doesnot result in hair loss, although temporary alopecia is seen in patients with heavy scaling. Long lasting cases with severe hyperkeratotic scalp may rarely induce scarring alopecia. On top of the physical symptoms, scalp psoriasis produces substantial negative psychosocial impact on the quality of life.

Frequently scalp psoriasis advances beyond the scalp margin. The retroauricular and posterior scalp (ie,. areas of easy assessibility) are commonly involved sites in scalp psoriasis.

A distinct morphological entity characterised by plaques of asbestos like scaling, firmly adherent to the scalp is known as pityriasis (tinea) amiantacea. It is more commonly seen in children and young adults. Although, it is described as an early manifestation of psoriasis, it is best regarded as a non-specific reaction pattern of the scalp to various inflammatory scalp diseases.

It is believed that pityrosporum spp. may be involved in the pathogenesis of scalp psoriasis. Systemic and topical antifungals have been shown to have a benefical effect on scalp psoriasis. On the other hand seborrheic dermatitis may be clinically and histologically indistinguishable from scalp psoriasis and severe seborrheic dermatitis can develop into psoriasis via a koebner phenomenon. The term ‘ sebopsoriasis’ is used to describe such overlap of psoriasis and seborrheic dermatitis.

MANAGEMENT:

The management of scalp psoriasis is a common problem seen by dermatologists almost daily. Not only does hair interfere with a convenient application of topical medications, but it also shields the skin from ultraviolet light, thus denying scalp psoriasis the benefits of natural sunlight and making photo-therapy impossible.

As in psoriasis in general, scalp psoriasis lesions can be controlled but cannot be cured yet. Therefore treatment should be safe and convient to the patient so that it can be continued lifelong.

The treatment options for scalp psoriasis can be broadly classified in to the following

a) Topical therapy.

b) Systemic therapy, and

c) Phototherapy.

1. Topical therapy.
   

Topical therapies are the mainstay of treatment of scalp psoriasis. The therapeutic options available are

1) Corticosteroids.

2) Vitamin D3 Analogues.

3) Keratolytics.

4) Coal tar.

5) Antimycotics.

6) Dithranol.

7) Tazarotene.

CORTICOSTEROIDS:

Topical corticosteroids remain the most commonly used treatment option of scalp psoriasis. Their mechanism of action includes vasoconstriction, anti-inflammatory, immunomodulatory effects and a dcrease of epidermal mitotic activity.Topical corticosteroid are subdivided based on potency. The high potent preparations are used in adults, these are clobetasol propionate (0.05%), betamethasone dipropionate (0.05%), and desoximetasone (0.25%). The low potency steroids like hydrocortisone butyrate (0.1%), methylprednisolone acetonate (0.1%), and perdnicarbate (0.1%) are preferred in children.

Adverse effects seen mainly are folliculitis, telangiectasia, skin atropy and suppression of HPA axis. Vehicles like gels and foams, which donot leave a greasy residue are used. It is advised to apply them overnight and wash off the next morning.

To reduce the adverse effects, intermittent use (3 to 4 times per week) is recommended. No data is available to support safety of these drugs on prolonged use. Hence, their use of more than 4 weeks is not recommended.

VITAMIN D₃ ANALOGUES:

Vitamin D₃ analogues available are calcipotriol, tacalcitol, maxacalcitol and caltriol. Most widely available agent is calcipotriol (50 mcg/g). It is available ointment, cream and lotion formulation. These agents have an effect on the proliferation and differentiation of epidermal cells and also on the immunological features of psoriatic lesions. Facial irritation is the major adverse effect seen. It can be combined with topical steroids for greater efficacy.

KERATOLYTICS:
These agents are indicated for patients with thick adherent scales and in pityriasis amiantacea. They allow penetration of other topical agents. Usually 5 to 15% salicylic acid in an ointment base is used. They are applied onto the whole scalp every night and washed off the next morning.

COAL TAR:

Tar is a mixture of thousands of substances produced by primary condensation during carbonization of coal. It reduces pruritus and also reduces epidermal hyperproliferation and inflammation. Crude tar is not suitable for scalp for cosmetic reasons but the alcoholic extract, solution carbonis detergens, can be used as 5 to 20% shampoos and lotions.

ANTIMYCOTICS:

As stated above, topical and systemic antifungals have shown to be effective in scalp psoriasis. Ketoconazole, selenium sulfide and zinc pyrithione are the most commonly used agents.

DITHRANOL:
Dithranol is usually used in inpatient departments as a short contact regimen. It is applied as a cream base and washed off after a specified contact period. It is known to induce long periods of remission. The two main adverse effects are local staining and irritation.

TAZAROTENE:

It is available as a 0.1% gel. It has shown good clinical efficacy and patient acceptance. The major draw back of tazarotene is local irritation at the site of application.

SYSTEMIC THERAPY:

Systemic therapies like methotrexate, acitretin and cyclosporine are indicated in patients with severe psoriasis. However evidence-based data on the efficacy and tolerability of systemic treatment for scalp psoriasis is sparse.

PHOTOTHERAPY:

UV-comb ( UVA or UVB) with optical fibres circumvents the hair which acts as a barrier to light and is able to deliver light directly onto scalp skin. It has an efficacy comparable to betamethasone valerate. It is currently not a popular treatment.

CONCLUSION:

The scalp is a predilection site of the common skin disease, psoriasis. The therapeutic arsenal for scalp psoriasis is extensive; the most important are topical corticosteroids and topical vitamin D3 derivatives. Since the treatment is chronic, education and emotional support are also important aspects in therapeutic approach.