Psoriasis

General Information

Classification: Integumentary

What is it?

Autoimmune disease of skin, nails, and joints that most commonly presents with well-demarcated silvery scales and plaques (especially over extensor surfaces, scalp, lumbarsacral region)

Risk Factors: genetic (PSOR1 on CHR6, HLA-Cw6), infections (Streptococcus), hypocalcemia, drugs (antimalarials, beta blockers, lithium), systemic steroid withdrawal, women, seasonal (aggravated in winter)

Evaluation

  • Symptoms: plaques, pustules, erythema, pain, pruritus
  • Lab biomarkers:
    • Rheumatoid factor: negative
    • CBC, comprehensive metabolic panel for renal/liver function tests
    • Elevated ESR, uric acid

Types

  • Type I: positive family history, <40 yr, associated with HLA-Cw6
  • Type 2: no family history, >40 yr, no HLA association
  • Subtypes (see below)

Pathophysiology

  1. Helper T cell (Th1) activation, releasing inflammatory agents (TNFα, IFy, interleukins)
  2. Proinflammatory molecules stimulate keratinocyte proliferation, forming plaques
  3. Erythema stimulated from overexpression of antimicrobial peptides
  4. Little oil/sebum production results in scales

Major Subtypes

Plaque

Most common subtype (85-90% of patients)

Erythematous plaques along extensor surfaces (elbows, knees, scalp) that often worsen in winter

Symmetrical (bilateral) distribution

Auspitz sign: bleeding points upon removal of scales

Figure 1 Plaque psoriasis affecting palm skin (Source: OpenI, NLM)

Guttate (Eruptive)

Common secondary to upper respiratory tract infection (primarily Strep)

Most common in adolescents or young adults

Small, scattered erythematous, raindrop-shaped lesions over the trunk and back

Figure 2 Guttate psoriasis lesions primarily affect the trunk and back (Source: OpenI, NLM)

Pustular

Erythematous pus-filled lesions (pustules)

Can be localized (small patches) vs generalized/von Zumbusch (sterile pustules across the entire body; associated with hypocalcemia)

Often presents acutely with leukocytosis, fever, malaise

RFs: pregnancy, withdrawal from glucocorticoids

Figure 3 Pustular psoriasis presenting with postules and surrounding erythema (Source: OpenI, NLM)

Erythrodermic

Widespread inflammation (>90% body) with pain, pruritus, and swelling

Desquamative scales

Due to exacerbation of unstable plaque psoriasis and withdrawal from systemic steroids, leading to sepsis or insensible perspiration

Figure 4 Widespread erythematic psoriasis across trunk and arms (Source: OpenI, NLM)

Subtypes (cont.)

Inverse (flexural/intertriginous): sharply demarcated patches along skin folds (groins, armpits, intergluteal)

  • Presents without scales

Sebopsoriasis: red plaques with greasy scales along thin skin (with sebaceous glands

Nail manifestations (see here): pitting, leukonychia, oil drop signs

Other signs

  • Koebner phenomenon: new papules at the site of previous trauma
  • Woronoff ring: blanching area around resolving plaques

Histological Characteristics

Acanthosis

Parakeratosis with neutrophil aggregation

Alternating hypogranulosis and hypergranulosis

Absence of granular lesions

Dilated and tortuous capillaries in the dermis

Figure 5 Psoriasis with hypogranulosis and neutrophil invasion in stratum corneum (Source)

Treatment

Topical

  • Corticosteroids, Vitamin D analogs, coal tar
  • Emollients and moisturizer for barrier function

Systemic: methotrexate, cyclosporine (especially with nail involvement)

Biologic: TNF inhibitors, IL12/17/23 inhibitors

Light therapy: UVB, PUVA (311-313 nm)

Comments!

Leave a comment

More posts