Psoriasis is a chronic, immune-mediated disease that affects approximately 2% of the population. The development and exacerbation of psoriasis involve an interaction between multiple genetic and environmental risk factors.

Psoriasis presents as well-circumscribed, erythematous plaques with an overlying silvery white scales. It has an effect on various aspects of life including mental health, productivity and relationships.

Topical therapies as corticosteroids and vitamin D3 analogs are first-line treatments for mild plaque psoriasis; which involves less than 3% of the body surface area (BSA). Moderate-to-severe plaque psoriasis is usually managed with phototherapy, systemic or biologic therapies .

The American Academy of Dermatology gives a strength recommendation for the use of combination therapies for treatment of psoriasis with superior efficacy to monotherapy .

The 308-nm excimer laser has been widely used for many dermatological diseases. In psoriasis, it shows an efficacy in the treatment of localised plaques especially on the knees and elbows.

It is indicated in moderate to severe psoriasis that affects <10% of the body surface. Areas such as nose, ears and palpebral region can be easily accessed using the laser. It induces lymphocytic apoptosis and decreases the proliferation rate of keratinocytes . There are multiple protocols that evaluate the clinical response to Excimer laser; the induration protocol, the minimal erythema dose and the minimal blistering dose.

The induration protocol compared with the others, allows to modify the dose with treatment. With this protocol, plaques achieved Psoriasis area and severity index (PASI-75) after 10 treatments .

Tazarotene (TAZ) is a topical retinoid with retinoic acid receptor β / γ receptor specificity. It has been shown to be effective for psoriasis treatment. However, its topical application is limited by its irritation.

Studies have shown that combination with other lines may optimize the efficacy as well as minimize the local irritation due to TAZ.

Betamethasone valerate (BV) is a high-potency, synthetic corticosteroid which acts on the intracellular glucocorticoid receptor.

It also binds to membrane-bound receptors, enhancing its action. BV suppresses the production of inflammatory cytokines and reduces keratinocyte hyperproliferation.

Inclusion Criteria:

1. Age: ≥18 years.
2. Pattern: Patients with chronic plaque psoriasis not exceeding 10% of the body surface area.

Exclusion Criteria:

1. History of retinoid use either topical or systemic in the previous 16 weeks, phototherapy or topical psoriasis treatment within the last 4 weeks.
2. Allergy to any ingredients of tretinoin or betamethasone drugs.
3. Renal, hepatic disease, cardiovascular , Immunosuppressive therapy, endocrine and blood disease or mental illness.
4. Pregnancy, breast-feeding or women planning to become pregnant within 3 months.
5. Psoriasis exceeding 10% of body surface area or other severe types of psoriasis requiring systemic treatment.
6. Patients with other diseases and requiring treatment that would affect the study