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Psoriasis

BASICS

  • Chronic inflammatory skin disorder with various phenotypes and severity.
  • Classic lesion: Well-demarcated erythematous plaques with silvery scale.
  • Phenotypes:
  • Plaque (vulgaris): ~80% of cases; symmetrical on scalp, extensors, trunk.
  • Guttate: <2%, abrupt onset, droplet-shaped papules, often post-strep infection.
  • Inverse: Intertriginous/flexural pink-red plaques, minimal scale.
  • Erythrodermic: Generalized erythema/scaling (>90% BSA), systemic symptoms.
  • Pustular: Sterile pustules, life-threatening in generalized type.
  • Nail involvement: Pitting, oil spots, onycholysis; up to 90% over lifetime; increased arthritis risk.

EPIDEMIOLOGY

  • Incidence: Two peaks—ages 20–30 & 50–60 years.
  • Prevalence: ~3.2% US population; most common in non-Hispanic Caucasians.

ETIOLOGY & PATHOPHYSIOLOGY

  • Immune-mediated with T-cell/dendritic cell/neutrophil/keratinocyte interplay.
  • Genetic predisposition: Polygenic, 40% have 1st-degree relative, HLA-C*06 associated with early onset.
  • Environmental triggers: Infection, trauma, drugs, stress, obesity.

RISK FACTORS

  • Family history
  • Obesity
  • Trauma (Koebner phenomenon)
  • HIV, strep infection
  • Stress, smoking, alcohol
  • Medications (lithium, antimalarials, β-blockers, interferon, TNF-α inhibitors, steroid withdrawal)
  • Gut microbiota dysbiosis

GENERAL PREVENTION

  • Control cardiovascular risk factors
  • Avoid known triggers (trauma, sunburn, smoking, certain drugs, alcohol, stress)
  • Healthy diet (limit saturated fats, sugars, red meats)

COMMONLY ASSOCIATED CONDITIONS

  • Psoriatic arthritis
  • Seborrheic dermatitis
  • Metabolic syndrome, obesity, diabetes, CKD
  • Cardiovascular & atherosclerotic disease
  • NAFLD
  • Other autoimmune: Crohn, UC, ankylosing spondylitis
  • Depression, anxiety, poor self-esteem, substance abuse
  • Myopathy

DIAGNOSIS

History

  • Sudden or chronic onset of sharply demarcated erythematous plaques, silvery scale, especially on extensor surfaces/scalp
  • Mild/no pruritus
  • Triggers: infection, trauma, medications
  • Family history

Physical Exam

  • Salmon pink-to-red plaques, silvery scale (scalp, extensor extremities, trunk, nails, etc.)
  • Nail findings: pitting, oil spots, onycholysis
  • Auspitz sign: pinpoint bleeding with scale removal
  • Koebner phenomenon: new lesions at trauma sites
  • Woronoff ring: pale blanching ring around lesions
  • Sebopsoriasis: overlap with seborrheic dermatitis

Differential Diagnosis

  • Plaque: seborrheic dermatitis, nummular eczema, atopic/contact dermatitis, tinea, pityriasis rubra pilaris, SCC in situ, dermatomyositis, reactive arthritis, pityriasis rosea, lichen planus
  • Guttate: secondary syphilis, pityriasis rosea, parapsoriasis
  • Inverse: candidiasis, tinea, seborrheic/contact dermatitis
  • Pustular: subcorneal pustulosis, exanthematous pustulosis, folliculitis
  • Erythrodermic: CTCL, drug erythroderma, pityriasis rubra pilaris

Diagnostic Tests

  • Clinical diagnosis; KOH prep (if tinea suspected, esp. inverse type)
  • Biopsy rarely needed unless unclear
  • X-ray if joint pain (psoriatic arthritis)
  • Scores: PASI (severity/BSA), DLQI (QoL impact)
  • Biopsy findings: Hyperkeratosis, parakeratosis, elongated rete ridges, dilated capillaries, perivascular lymphocytes, Munro abscesses (neutrophils in stratum corneum)

TREATMENT

General Measures

  • Adequate skin hydration (emollients)
  • Avoid triggers; weight loss

First Line (by severity)

Mild-to-moderate

  • Emollients: petrolatum/ointments
  • Topical corticosteroids:
  • Medium potency for most adults (mometasone, triamcinolone)
  • High/superpotent for recalcitrant plaques (clobetasol, halobetasol; limit duration)
  • Low potency for face/flexures/children (1% hydrocortisone)
  • Avoid occlusive dressings unless specified
  • Vitamin D analogues: calcipotriene 0.005% cream daily–BID (may combine with steroid)
  • Topical retinoids: tazarotene 0.05–0.1% (may combine with steroid; avoid in pregnancy)
  • Topical calcineurin inhibitors: tacrolimus/pimecrolimus for face/flexures
  • Scalp: high-potency steroids in solutions/foams; medicated shampoos

Moderate-to-severe or extensive

  • Phototherapy: UVB (broad/narrowband), PUVA (skin-type dependent, cancer risk)
  • Systemic therapies:
  • Methotrexate: 7.5–25 mg/week (test dose, titrate), monitor CBC, LFTs, renal, TB, pregnancy contraindication
  • Cyclosporine: 2.5–5 mg/kg/day (renal toxicity, HTN, limit duration)
  • Acitretin: 10–25 mg/day (pustular type, teratogenic—pregnancy X)
  • Apremilast: up to 30 mg BID (GI symptoms, depression, expensive)
  • Biologics: For moderate/severe or psoriatic arthritis (screen for TB/hepatitis, avoid live vaccines, monitor for infection/malignancy)
  • TNF-α inhibitors: etanercept, adalimumab, infliximab, certolizumab
  • IL-12/23 antagonist: ustekinumab
  • IL-17 antagonists: secukinumab, brodalumab, ixekizumab (avoid in IBD)

Second Line

  • Immunosuppressives: azathioprine, hydroxyurea, 6-thioguanine, fumaric acid esters
  • Topicals: salicylic acid, anthralin, coal tar

Special Considerations

  • Assess for psoriatic arthritis; prioritize agents with joint benefit
  • Combination therapy (superpotent steroids + vit D analogues) often best
  • Severe/refractory/extensive disease: Refer to dermatology

REFERRAL / SURGERY

  • Dermatology for >20% BSA, psoriatic arthritis, pustular, severe extremity involvement, or refractory to topicals
  • Surgery: Consider perioperative medication effects on wound healing

COMPLEMENTARY & ALTERNATIVE

  • Balneotherapy, climatotherapy, stress management

ADMISSION/INPATIENT CARE

  • For erythrodermic/pustular/severe disease: monitor for sepsis, restore skin barrier, intensive topicals, systemic therapy, manage electrolytes

ONGOING CARE

  • Regularly assess BSA/severity; adjust therapy if inadequate response

DIET

  • Heart-healthy; limit saturated fats/sugars/red meats
  • Encourage fatty fish; adjunct only

PATIENT EDUCATION

PROGNOSIS

  • Guttate: often self-limited
  • Chronic plaque: lifelong with remissions/exacerbations
  • Erythrodermic/generalized pustular: may be severe/persistent

COMPLICATIONS

  • Psoriatic arthritis, generalized pustular/erythrodermic forms
  • Cardiovascular disease

ICD-10 Codes

  • L40.2 Acrodermatitis continua
  • L40.5 Arthropathic psoriasis
  • L40.59 Other psoriatic arthropathy

CLINICAL PEARLS

  • Lifelong, relapsing disease; set realistic expectations.
  • Disease burden extends beyond skin (joints, cardiovascular, psychological).
  • Control CV risk factors; monitor for associated conditions.