One-liner#

Chronic immune-mediated inflammatory skin disease characterized by well-demarcated erythematous plaques with silvery scale, requiring ongoing management with topical therapy for limited disease and systemic therapy for moderate-severe disease, with screening for psoriatic arthritis and metabolic comorbidities.

Quick nav#

• Definition and epidemiology
• Pathophysiology
• Clinical presentation
• Diagnostic workup
• Treatment
• Patient education
• Prognosis and monitoring
• Special populations
• When to refer
• Smartphrase snippets
• Related pages

Definition and epidemiology#

Diagnostic criteria#

Clinical diagnosis based on characteristic findings:

• Well-demarcated erythematous plaques with silvery-white scale
• Typical distribution: extensor surfaces (elbows, knees), scalp, sacrum, umbilicus
• Auspitz sign: pinpoint bleeding when scale removed
• Nail changes: pitting, onycholysis, oil spots
• Koebner phenomenon: new lesions at sites of skin trauma

Biopsy rarely needed but shows: acanthosis, parakeratosis, Munro microabscesses, dilated capillaries in dermal papillae.

Epidemiology#

• Prevalence: 2-3% of population; affects ~8 million Americans
• Bimodal onset: peak at 20-30 years and 50-60 years
• Equal male:female ratio
• Strong genetic component: 30% have first-degree relative with psoriasis
• Risk factors: family history, obesity, smoking, stress, certain medications (lithium, beta-blockers, antimalarials)
• Associated conditions: psoriatic arthritis (up to 30%), metabolic syndrome, cardiovascular disease, depression

Pathophysiology#

Mechanism (clinical understanding)#

Psoriasis is a T-cell mediated autoimmune disease with dysregulated immune response:

1. Initiation: Trigger (infection, trauma, stress, medication) activates dendritic cells
2. T-cell activation: Dendritic cells present antigens to T-cells, activating Th1 and Th17 pathways
3. Cytokine cascade: IL-17, IL-23, TNF-alpha drive inflammation
4. Keratinocyte hyperproliferation: Normal skin turnover is 28-30 days; in psoriasis it’s 3-5 days
5. Plaque formation: Rapid turnover causes accumulation of immature keratinocytes (scale) with underlying inflammation (erythema)

Why this matters for treatment:

• Topical steroids reduce inflammation
• Vitamin D analogs slow keratinocyte proliferation
• Biologics target specific cytokines (TNF-alpha, IL-17, IL-23)
• Systemic inflammation explains cardiovascular and metabolic comorbidities

How to explain to patients#

“Psoriasis is a condition where your immune system is overactive and causes your skin cells to grow too fast. Normally, skin cells take about a month to mature and shed. In psoriasis, this happens in just a few days, so the cells pile up and form thick, scaly patches. It’s not contagious—you can’t catch it or give it to anyone. It’s a lifelong condition, but we have very effective treatments to control it. Because the same inflammation affects other parts of your body, we also watch for joint problems and heart health.”

Clinical presentation#

Characteristic symptoms#

Plaque psoriasis (most common, 80-90%):

• Well-demarcated, raised, erythematous plaques
• Silvery-white scale that sheds
• Symmetric distribution
• Pruritus in ~80% (can be severe)
• Burning or soreness, especially with cracking

Distribution patterns:

• Classic: elbows, knees, scalp, sacrum, umbilicus
• Scalp: thick scale, often extends beyond hairline
• Inverse: flexural areas (axillae, groin, inframammary)—less scale, more erythema
• Palmoplantar: painful, fissured plaques on palms/soles
• Nail: pitting, onycholysis, oil spots, subungual hyperkeratosis

Other variants:

• Guttate: small drop-like lesions, often post-streptococcal
• Pustular: sterile pustules, can be localized or generalized (severe)
• Erythrodermic: >90% BSA involvement (medical emergency)

Physical exam findings#

• Plaques: Well-demarcated, raised, erythematous with silvery scale
• Auspitz sign: Pinpoint bleeding when scale removed (don’t routinely test—causes discomfort)
• Nail changes: Pitting (ice pick depressions), onycholysis, oil drop sign, subungual hyperkeratosis
• Scalp: Thick adherent scale, often at hairline
• Body surface area (BSA): Palm = 1% BSA; estimate total involvement
  • Mild: <3% BSA
  • Moderate: 3-10% BSA
  • Severe: >10% BSA

Red flags#

• Erythroderma (>90% BSA): Medical emergency—risk of hypothermia, infection, high-output cardiac failure
• Generalized pustular psoriasis: Fever, sterile pustules, systemic illness—hospitalization required
• Joint symptoms: Morning stiffness >30 minutes, joint swelling, dactylitis (“sausage digits”)—screen for psoriatic arthritis
• Rapid worsening after stopping systemic steroids: Rebound flare, can trigger pustular or erythrodermic psoriasis

Diagnostic workup#

Initial evaluation#

Clinical diagnosis—no routine labs needed for typical plaque psoriasis.

Assess at initial visit:

• Body surface area involvement
• Location (high-impact areas: face, hands, genitals, scalp)
• Quality of life impact (Dermatology Life Quality Index if available)
• Joint symptoms (PEST questionnaire or direct questioning)
• Nail involvement
• Prior treatments and response

Confirmatory testing#

Skin biopsy: Only if diagnosis uncertain

• Atypical presentation
• Not responding to treatment
• Concern for cutaneous T-cell lymphoma

Labs to consider:

When to refer for specialist workup#

• Uncertain diagnosis
• Moderate-severe disease (>10% BSA or high-impact areas)
• Failure of topical therapy after 8-12 weeks
• Need for systemic therapy or phototherapy
• Suspected psoriatic arthritis (co-manage with rheumatology)
• Pustular or erythrodermic psoriasis (urgent)

What NOT to order#

• Routine skin biopsy for classic plaque psoriasis—clinical diagnosis is sufficient
• Extensive autoimmune panels (ANA, RF)—psoriasis is not associated with these
• Allergy testing—psoriasis is not allergic in nature
• “Psoriasis blood test”—does not exist; diagnosis is clinical

Treatment#

Goals of therapy#

• Clear or near-clear skin (BSA <1% or PASI 90 response)
• Improve quality of life
• Prevent joint damage (if psoriatic arthritis present)
• Reduce cardiovascular risk through inflammation control
• Minimize treatment side effects

Realistic expectations:

• Topical therapy: 50-75% improvement in 4-8 weeks
• Systemic therapy: 75-90% improvement in 12-16 weeks
• Complete clearance possible with biologics
• Chronic condition requiring ongoing treatment

Non-pharmacologic management#

Skin care:

• Daily moisturization with thick emollients (petrolatum, ceramide creams)
• Lukewarm baths with colloidal oatmeal or bath oils
• Gentle scale removal: soak, then gently remove with soft cloth (don’t pick)
• Avoid skin trauma (Koebner phenomenon)

Trigger avoidance:

• Stress management (meditation, exercise, adequate sleep)
• Smoking cessation (smoking worsens psoriasis and reduces treatment response)
• Limit alcohol (worsens psoriasis, interacts with methotrexate)
• Avoid medications that trigger flares: lithium, beta-blockers, antimalarials, NSAIDs (in some patients)

Weight management:

• Obesity worsens psoriasis severity
• Weight loss improves treatment response
• 5-10% weight loss can significantly improve disease

Sun exposure:

• Moderate sun exposure often helps (natural UV therapy)
• Avoid sunburn (can trigger Koebner phenomenon)
• Some patients have photosensitive psoriasis (rare)

Pharmacologic management#

Mild disease (<3% BSA):

Scalp psoriasis:

Moderate-severe disease (>10% BSA or high-impact areas)—Dermatology referral recommended:

Biologics (specialist-initiated):

Patient counseling points#

For topical steroids: “Apply a thin layer to the red, scaly patches only—not to normal skin. Use it for 2-4 weeks, then take a break to prevent skin thinning. Don’t use strong steroids on your face or skin folds.”

For calcipotriene: “This is a vitamin D-based cream that slows down skin cell growth. It works well with steroids. Apply it to the plaques twice daily. It may cause some irritation initially—this usually improves with continued use.”

For methotrexate: “This medication calms down your immune system. Take it once a week—not daily. Take folic acid every day to reduce side effects. Avoid alcohol completely while on this medication. You’ll need regular blood tests to monitor your liver and blood counts. Don’t get pregnant while taking this.”

For biologics: “These are targeted medications that block specific parts of the immune system causing psoriasis. They’re very effective—most people see significant clearing. They’re given as injections, usually at home. Because they affect your immune system, we screen for infections before starting and you should avoid live vaccines.”

Monitoring and follow-up#

Topical therapy:

• Follow-up in 4-8 weeks to assess response
• If inadequate response, step up therapy or refer to dermatology
• Once controlled, follow-up every 3-6 months

Systemic therapy (methotrexate):

• CBC, LFTs, Cr at baseline
• Repeat at 1 month, then every 3 months
• Consider liver biopsy or FibroScan after cumulative dose of 3.5-4g

Biologics:

• TB screening (PPD or IGRA) before starting
• Hepatitis B/C screening before starting
• Monitor for infections at each visit
• Annual TB screening if ongoing risk factors

All patients:

• Screen for psoriatic arthritis at every visit (joint pain, stiffness, swelling)
• Annual cardiovascular risk assessment (lipids, glucose, BP)
• Depression screening (PHQ-2/PHQ-9)
• Skin cancer screening (increased risk with phototherapy)

Patient education#

What is this condition?#

Psoriasis is a skin condition where your immune system causes skin cells to grow too fast. Instead of taking a month to mature and shed, skin cells do this in just a few days. This causes thick, red, scaly patches on your skin.

Psoriasis is not contagious. You cannot catch it from someone or give it to anyone else. It tends to run in families and is a lifelong condition, but it can be well controlled with treatment.

What you can do#

• Moisturize your skin daily, especially after bathing. Use thick creams or ointments.
• Take lukewarm baths or showers. Hot water can dry out your skin and worsen psoriasis.
• Gently remove scales after soaking. Don’t pick or scratch—this can make psoriasis worse.
• Manage stress through exercise, relaxation, or activities you enjoy. Stress can trigger flares.
• If you smoke, work on quitting. Smoking makes psoriasis worse and reduces how well treatments work.
• Limit alcohol, especially if you’re on certain medications.
• Maintain a healthy weight. Extra weight can worsen psoriasis.
• Get some sun, but don’t burn. Moderate sun exposure often helps psoriasis.

When to seek care#

• Your psoriasis is spreading or getting worse despite treatment
• You develop joint pain, stiffness, or swelling (could be psoriatic arthritis)
• Your skin becomes very red over large areas of your body
• You develop fever with your skin symptoms
• Your treatment is causing bothersome side effects
• Your psoriasis is affecting your quality of life or mood

Questions to ask your doctor#

• What type of psoriasis do I have?
• How much of my body is affected?
• Should I be checked for psoriatic arthritis?
• What are my treatment options?
• How long until I see improvement?
• What are the side effects of my treatment?
• Do I need any blood tests?
• Should I see a dermatologist?
• What can I do to prevent flares?

Prognosis and monitoring#

Expected course#

• Chronic, lifelong condition with periods of flare and remission
• Most patients can achieve good control with appropriate treatment
• ~30% develop psoriatic arthritis (can occur before, with, or after skin disease)
• Spontaneous remission occurs in ~20% but usually temporary
• Severity often stable over time, but can worsen with triggers

With treatment:

• Topical therapy: 50-75% improvement expected in 4-8 weeks
• Systemic therapy: 75-90% improvement in 12-16 weeks
• Biologics: 80-90% can achieve clear or almost clear skin

Monitoring parameters#

Complications to watch for#

• Psoriatic arthritis: Joint pain, stiffness, swelling, dactylitis—refer to rheumatology
• Cardiovascular disease: Increased risk of MI, stroke—aggressive risk factor management
• Metabolic syndrome: Obesity, diabetes, dyslipidemia—screen and treat
• Depression/anxiety: Common comorbidity—screen and treat
• Skin cancer: Increased risk with phototherapy—annual skin exams
• Medication side effects: Liver toxicity (methotrexate), infections (biologics)

Special populations#

Elderly/geriatric#

• More likely to have comorbidities affecting treatment choice
• Increased infection risk with biologics—weigh benefits vs risks carefully
• Methotrexate: start lower dose (7.5 mg/week), monitor renal function closely, increased toxicity risk
• Avoid cyclosporine if possible due to nephrotoxicity and hypertension risks
• Topical therapy often preferred if disease limited
• Consider polypharmacy and drug interactions with all systemic agents
• Beers criteria: avoid first-generation antihistamines for pruritus

Chronic kidney disease#

• Methotrexate: Avoid if eGFR <30; reduce dose if eGFR 30-60
• Cyclosporine: Avoid—nephrotoxic
• Apremilast: Reduce dose to 30 mg daily if eGFR <30
• Biologics: Generally safe; no dose adjustment needed
• Topical therapy: Safe; preferred for limited disease

Pregnancy and lactation#

• Many systemic treatments contraindicated
• Safe in pregnancy: Topical steroids (low-mid potency), emollients, UVB phototherapy
• Avoid in pregnancy: Methotrexate (teratogenic—stop 3 months before conception), acitretin (stop 3 years before), tazarotene
• Limited data: Biologics—certolizumab has most safety data; discuss with dermatology/MFM
• Psoriasis often improves during pregnancy, may flare postpartum

Other populations#

Psoriatic arthritis:

• Affects up to 30% of psoriasis patients
• Can cause permanent joint damage if untreated
• Screen at every visit: morning stiffness >30 min, joint pain/swelling, dactylitis, enthesitis
• PEST questionnaire: ≥3 positive answers suggests PsA
• Treatment: NSAIDs for mild; DMARDs (methotrexate) or biologics for moderate-severe
• Co-manage with rheumatology

Polypharmacy considerations:

• Methotrexate: multiple drug interactions (NSAIDs increase toxicity, trimethoprim increases bone marrow suppression)
• Biologics: avoid live vaccines
• Review all medications before starting systemic therapy

When to refer#

Specialist referral criteria#

Dermatology referral:

• Moderate-severe disease (>10% BSA)
• High-impact areas (face, hands, genitals) not responding to topical therapy
• Failure of topical therapy after 8-12 weeks
• Need for phototherapy or systemic therapy
• Uncertain diagnosis
• Pustular or erythrodermic psoriasis

Rheumatology referral:

• Suspected psoriatic arthritis (joint pain, swelling, stiffness, dactylitis)
• PEST score ≥3
• Inflammatory back pain

Urgency levels#

• Routine (weeks): Moderate disease, topical failure, need for systemic therapy
• Urgent (days): Rapidly worsening disease, suspected psoriatic arthritis with joint damage concern
• Emergent (same day): Erythrodermic psoriasis, generalized pustular psoriasis, severe drug reaction

Smartphrase snippets#

Stable/controlled: Psoriasis well-controlled on current regimen, BSA approximately [X]%. No joint symptoms on screening. Continue current therapy and follow-up in [3-6 months].

Worsening/uncontrolled: Psoriasis flare with BSA increased to [X]%, triggers include [stress/infection/unknown]. Plan to [intensify topical therapy / refer to dermatology]. Follow-up in [4-6 weeks].

New diagnosis: New diagnosis of plaque psoriasis, BSA approximately [X]% affecting [locations]. Screened for psoriatic arthritis—negative. Starting [topical regimen] with follow-up in [6-8 weeks].

Related pages#

• Rash (Chronic/Recurrent) (complaint) — symptom-based approach to chronic rashes including psoriasis differential
• Atopic Dermatitis (problem) — another common chronic inflammatory skin condition