Psoriasis

PathologyKeratinocyte hyperproliferation: differentiation, or ‘skin cell going from basal layer to horny layer’, reduced from 4 weeks to 4 days [approximately!]
Histopathological features:

• Parakeratosis: retained nuclei
• Acanthosis: thick epidermis
• Absent granular layer
• Lengthened rete ridges
• Thin dermal papillae
• Dilated, tortuous capillaries
• Munro’s micro-abscesses
• T-cells in upper dermis

 

Clinical featuresAge: 15-40 years; esp. in 30s
Types

• Classical [or typical]
  • Plaques: Well-circumscribed erythematous plaques with silver scaling
  • Distribution: Esp. on extensor surfaces [elbow, knee], scalp/hairline, sacral
  • Features: Pain, itch [but less than eczema/dermatitis]
  • Auspitzs sign: Bleeding on scale removal
• Guttate
  • Age: Young
  • Onset: Follows streptococcal tonsillitis
  • Plaques: Multiple discoid erythematous and scaly macules and plaques on trunk
• Palmoplanar pustular
  • Plaques: Yellow-brown pustules on palms and soles
• Flexoral
  • Plaques: Erythematous, but not scaly
  • Distribution: Submammary, axillary, anogenital, umbilical
  • Epidemiology: Esp. women; also the elderly and HIV +ve
• Erythrodermic [emergency!]
  • Features: Acute onset of erythroderma and pustular plaques
  • Management: Methotrexate
  • Others: only scales; only nails; and napkin

Nails

• Features: Pitting, onycholysis [nail lifting off the bed]; subungal hyperkeratosis; Beaus lines [horizontal, across the nail]
• Differential diagnosis: fungal infection, alopecia areata

Psoriatic arthropathy

• Patterns: [1] AnkSpond-like/spondylitis; [2] RA-like/symmetrical; [3] Asymmetrical, <3 joints;[4] DIP joints, hands; [5] Arthritis multilans

Differential diagnosis

• Dermatitis/eczema: discoid or seborrhoeic
• Lichen planus
• Pityriasis rosea [esp. guttate psoriasis]
• 2^o stage of syphilis
• Reiter’s syndrome [Esp. palmoplanar psoriasis]
• Discoid lupus

 

Precipitating factors

• Trauma [known as Koebner’s phenomena]
• Drugs: β-blockers, lithium, anti-malarials; NSAIDs and ACE-Is
• Stress
• Sunlight
• ‘Genetic’

 

ManagementTopical

• Emollients
• Vit. D analogues
  • Calcipotriol, tacalcitol and calcitriol
  • Mechanism: ↓ cell proliferation
  • Side-effects: Skin irritation, hypercalaemia if overdose
• Coal tar preparations
  • Mechanism: Inhibit DNA synthesis
  • Problems: Smelly, messy
• Dithranol
  • Anthralin
  • Mechanism: ↓ cell proliferation
  • Side-effects: Irritates neighbouring normal skin, stains clothes purple
• Keratolytics
  • Salicylic acid
• Corticosteroids
  • Caution: Not alone, as may cause brittle psoriasis on rebound
• Retinoids
  • Tazarotene

Systemic

• Immunosuppressants
  • Methotrexate
  • Also ciclosporin, azathioprine, and hydroxyurea
• Retinoids
  • Acitretin
  • Note: Therapeutic effect after 4-6 weeks; used for <6 months
  • Side-effects
    • Teratogenic for up to 3 years
    • Dry mucous membranes: skin, eyes, lips [may cause epistaxis]
    • Others: hepatotoxicity; deranged lipid profile
• Photo[chemo]therapy
  • UVB for classic/plaque and guttate types
  • PUVA [psoralen] for palmoplanar type
• Treating classic/typical psoriasis
• 1^st line: Dithranol
• 2^nd line: Vit. D analogues or topical steroids + tar or salicylic acid ± UVB
• 3^rd line: Retinoids, PUVA + immunosuppressants
• Goekerman regime = Tar + UVB
• Ingram regime = Goekerman + dithranol

Reference: http://almostadoctor.co.uk/content/systems/dermatology/psoriasis

http://www.webmd.com/skin-problems-and-treatments/guide/skin-problems-treatments-symptoms-types