PSORIASIS
DEFINITION:
A chronic cutaneous disorder characterized by papules which
coalsce to form plaques covered by a thick silvery or yellow-white
scale.
EPIDEMIOLOGY:
- incidence: 1-2% of the population
- age of onset:
- 35% by age 20 years
- 10% by age 10 years
- 2% by age 2 years
- risk factors:
- F > M (2:1)
- whites > blacks, Asians, Indians
PATHOGENESIS:
- accelerated epidermal turnover results in the accumulation
of thick scales over the affected areas of skin
- most patients have mild disease limited to sites of frequent
trauma and irritation (knee, elbows, scalp, groin, sacrum)
2. Etiology
- while the etiology is unknown, the expression of the disease
seems to be dependent upon a susceptible host being exposed to
specific triggers:
3. Types of Psoriasis
- Plaque-Type
- Guttate
- Inverse
2. Minor
- Generalized Pustular (von Zumbusch type, Annular)
- Localized Pustular (Palmoplantar, Acrodermatits continua)
- Erythrodermic
CLINICAL FEATURES:
- round, red, dry, circumscribed plaques covered with a
silvery white, thick, adherent scale
- plaques range in size from 1-10 cm in diameter
- predilection for extensor surfaces of large joints,
sacrum, and scalp
- Ausptiz sign
- pinpoint bleeding upon intentional removal of lesion
- Woronoff's ring
- blanched area around the perimeter of a healing lesion
- Geographic tongue
- psoriasis manifested on the tongue
2. Guttate Psoriasis
- multiple discrete tear-shaped lesions covered with a
silvery scale (paint spray)
- lesions range from 0.5-1.5 cm in diameter
- predilection for the trunk, proximal extremities, and face
- usually triggered by a streptococcal infection, viral
infections, sunburn, and systemic corticosteroid withdrawal
- onset characterized by an explosive eruption of
erythematous macules which persist for 6-8 weeks
3. Inverse Psoriasis
- skin in affected areas become red and macerated but not
scaly
- predilection for intertriginous (axillae, gluteal cleft,
perineum) and diaper areas
2. Other Manifestations
- may be the sole manifestation of psoriasis
- pitting, leukonychia (white spots), longitudinal ridges
and grooves, tranverse depressions, reddish-brown
discolouration of the nailbed (oil spots),
- nail psoriasis
- crumbling of the nail bed
- hyperkeratosis (subungual debris)
- onycholysis (detachment of the nail)
2. Musculoskeletal
INVESTIGATIONS:
- thickened stratum corneum with perakeratosis (nuclei
retained in the stratum corneum)
- hyperplastic epidermis containing microabscesses
- increased vascularization and inflammation of the dermis
MANAGEMENT:
- avoid specific triggers (cold weather, infections, trauma)
- aggressive treatment of streptococcal infections
- penicillin, erythromycin
- five days of rifampin to decrease the rate of chronic
streptococcal carriage
- avoid dry skin with proper skin care
- daily baths with minimal use of mild soaps and cleaners
- thick lubricant or emollient over damp skin
- increase exposure to sun (but avoid sunburns)
- psychotherapy or group therapy for severe cases
2. Medications
- salicylic or lactic acid preparations (2-10%)
- should be incorporated into a bland, ointment-type vehicle
(white petrolatum or Aquaphor)
2. Tar Preparations
- mainstay of psoriasis therapy
- act by reducing epidermal cell DNA synthesis and mitotic
activity of the hyperplastic epidermis
- topical oils, emollients, and gels; shampoos
- crude coal tar (1-3%), liquor carbonis detergens (5-10%)
3. Topical Steroids
- low -> high potency (Class I agents)
- use 1-2.5% hydrocortisone to facial & intertriginous areas
- use 0.025-0.1% corticosteroid preparations to other areas
4. Others
3. Ultraviolet Radiation Therapy
- UVB
- UVA +/- psoralens (PUVA)
4. Scalp Psoriasis
- tar shampoos, keratolytics, moderate-potency topical steroid
solutions
- may apply topical steroid solutions to small affected areas
od or bid
5. Prognosis
- psoriasis is a chronic condition with flares and remissions
which may worsen with age
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