Psoriasis

Psoriasis 

Updated: 02/10/2021

© Jun Wang, MD, PhD

General features

• Chronic, multifactorial inflammation
• Common; affects 1-2% of population, all ages, slightly more common in women
• May be associated with arthritis, myopathy, enteropathy, and AIDS 
• Symptoms tend to wax and wane, associated with systemic and environmental factors
  
• Triggering factors

Cold

Trauma

Infections

Alcohol

Drugs

Stress

• Beneficial factors

Hot weather

Sun light

Pregnancy status

• Possibly life threatening if with fever, leukocytosis, diffuse infections, and electrolyte disturbances
• Usually clinical diagnosis
  

Pathogenesis

• Unclear, likely immune-mediated
  
• Increase in the epidermal cell turnover rate with accompanied activated T cell infiltration
• Elevated levels of cytokines, such as tumor necrosis factor-a, interferon-g, interleukin-12, interleukin-17
• Certain genetic factors: deletion of late cornified envelop genes, HLA-Cw6, obesity

Clinical features

• Either localized (hands/feet) or generalized 
• Five major types
• Plaque
• Inverse: flexural surfaces and skin folds, DDx dermatophytosis
  
• Guttate
• Erythrodermic: Widespread red skin with diffuse fine peeling scale
  
• Pustular
  
• Worsening or sudden onset
• Scaly area redness
• Pain (especially in erythrodermic psoriasis and psoriatic arthritis)
• Pruritus (especially in eruptive, guttate psoriasis)
• Dystrophic nails: pits on nails, thickening, yellowish discoloration
• Joint manifestation: Psoriatic arthritis, etc
• Ocular involvement: Conjunctivitis or blepharitis
• Auspitz sign: punctate bleeding spots when psoriasis scales are scraped off, non-specific

Plaque psoriasis

• Most common
• Rarely life threatening
• Commonly on extensor surfaces
  
• Raised well demarcated erythematous papules or plaques
• Dry, thin, silver to white scales

Guttate psoriasis

• Acute onset
• May have history of upper respiratory group A beta-hemolytic streptococci infection
  
• Small drop like erythematous to salmon-pink papules (Guttate as defined by Merriam-Webster: having small usually colored spots or drops)
• Fine scale
• Primarily on the trunk and proximal extremities
• DDx: Secondary syphilis 
  
• Likely to be self-limiting

Pustular psoriasis

• Widespread pustules on erythematous background
• Acute, subacute and chronic
• Acute generalized type usually accompanied by fever, may be life threatening if not managed properly

Psoriatic arthritis

• Common in patients with psoriasis 
• May occur before the onset of psoriasis
  
• Seronegative oligoarthritis
• Onset or exacerbation may be associated with trauma
• May start with stiffness and pain
• First affects DIP of hands and feet; similar to rheumatoid arthritis but milder
• Inflammation of digital tendon sheaths causes sausage fingers
• May develop erosive and deforming arthritis
  

Pathological features

• Parakeratosis without hyperkeratosis
• Thin/no granular cell layer
• Downward elongation of rete ridges
• Suprapapillary thinning
• Munro-microabscess: Clusters of neutrophils in parakeratotic scale

Management

• Immunosuppressant: methotrexate, cyclosporine, etc

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