Psoriasis vulgaris is a chronic skin disorder caused by accelerated mitosis and rapid epidermal cell turnover, leading to decreased cell maturation and abnormal keratinization. This rapid cell turnover prevents dermal cells from adhering properly, causing shedding in the form of characteristic silvery scales over underlying red plaques. Genetic and immunological factors drive its development, while environmental extremes, physical injury, and psychological stress often trigger disease flares. The condition is more prevalent in women, consistent with many other autoimmune diseases.
Disease severity is categorized according to Total Body Surface Area (BSA) involvement:
Clinical Concept: Forcible removal of psoriatic plaques can result in pinpoint bleeding, a classic phenomenon known as the Auspitz sign.
Psoriasis classically presents on extensor surfaces, with plaques most frequently localized over the knees and elbows. Other common sites include the scalp, extensor surfaces, genitals, umbilicus, and lumbosacral or retroauricular regions.
Differential Diagnosis: Conditions to consider in differential evaluation include blepharitis, allergic contact dermatitis, cutaneous squamous cell carcinoma, lichen planus, nummular dermatitis, onychomycosis, pityriasis rosea, and seborrheic dermatitis.
Diagnosis is based on patient history, risk factors (such as family history), and physical examination findings. When psoriatic arthritis is suspected, diagnostic testing helps differentiate it from rheumatoid arthritis and gout:
Therapy choice depends on disease severity, distribution, and response to previous treatments:
| Therapy Category | Agents / Modalities | Clinical Considerations & Adverse Effects |
|---|---|---|
| First-Line Topical | Topical Corticosteroids (medium- to high-potency short-term, stepping down to low-potency 3–4x weekly for maintenance) | Anti-inflammatory and antimitotic. Long-term use of high-potency steroids is discouraged due to risks of skin atrophy, telangiectasia, acne, striae, and systemic adrenal suppression. Ocular solutions can be used for ophthalmic involvement. |
| OTC Topicals | Coal Tar Preparations (shampoos, lotions, creams, foams) | Helpful adjunctive option, though patient adherence is limited by messiness and odor. |
| Second-Line Topicals | Anthralin (Drithocreme®), Calcipotriene (Vitamin D3 derivative), Tazarotene (retinoid prodrug) | Effective for controlling cell proliferation and inflammation; reserved for corticosteroid-resistant disease due to higher cost. |
| Phototherapy | Ultraviolet A (UVA) light (3x/week) | Highly effective for generalized disease (>30% BSA), but carries risks of photoaging and increased skin cancer risk. |
| Systemic & Oral Agents | Cyclosporine, Methotrexate, Acitretin (systemic retinoids), Apremilast (Otezla®) | Indicated for severe, recalcitrant disease or concurrent psoriatic arthritis. Apremilast is an oral PDE-4 inhibitor for moderate-to-severe plaque psoriasis. |
| Biologic Therapies | TNF-α Inhibitors (Etanercept/Enbrel®, Infliximab/Remicade®, Adalimumab/Humira®); IL Inhibitors (Secukinumab/Cosentyx®, Ixekizumab/Taltz®, Brodalumab/Siliq™, Ustekinumab/Stelara®) | Target inflammatory pathways. Associated with injection/infusion reactions, elevated infection risks, and potential reactivation of latent tuberculosis. Risk is heightened in patients with diabetes, heart failure, or co-administered immunosuppressants. |
Specialist referral to a dermatologist is recommended when a patient presents with severe disease (>10% BSA) or when milder disease fails to respond to standard initial therapies.
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