-IBIS-1.5.0-
tx
cutaneous system
psoriasis
diagnoses

definition and etiology

definition: a common, persistent, and recurrent skin disease with dry, well-circumscribed silvery, scaling papules and plaques of different sizes

etiology: Psoriasis is one of the most common skin diseases, affecting approximately 2-4% of the white population (fewer blacks are affected). Most patients experience the onset before the age 20, although the usual ages are between 10-40 years old. There seems to be a genetic tendency, as 30% of patients have a positive family history and certain HLA antigens are associated with the disease. Although the exact cause is unknown, one possible explanation for the development of psoriasis might be the abnormal ratio of cAMP to cGMP in the epidermis of the psoriatic patient; decreased cAMP and increased cGMP levels are present in affected individuals. Psoriasis is a hyper-proliferative disease, where the normal transit time of the epidermis decreases from 28 days to 3-4 days. The presentation can vary from 1-2 lesions, to a severe outbreak with accompanying arthritis and exfoliation.

signs and symptoms

signs and symptoms: onset is gradual; course of disease is marked by remissions and exacerbations of varying acuity
• only 30% of psoriasis patients experience itching of their lesions
• psoriasis is usually worse in winter from low humidity and lack of sunlight
• lesion presents as a well-circumscribed papule or plaque, with a characteristic salmon-red color and overlapping, silvery, slightly opaque, shiny scales
• removal of scale results in pinpoint bleeding (Auspitz sign)
• pustules might present along with inflammation; they are sterile and do not represent infection
• lesions heal without scarring, and do not affect hair growth
• if the nails become involved, they resemble fungus infections with pitting, fraying, thickening, discoloration, and debris under the nail bed

factors that can trigger a psoriatic eruption include:
• trauma to an area (the Koebner phenomenon)
• bad sunburns, irritation
• topical medications
• acute URI (esp. in children)

eruptions may be generalized over the entire body; areas particularly susceptible to psoriatic eruptions are:
• hairline of the scalp
• extensor surfaces of extremities: knees, elbows, wrists
• buttocks and sacrum
• occasionally, the eyebrows, axillae, nails (50% of patients have nail involvement), umbilicus and anogenital regions (psoriasis is the most common cause of pruritus ani)

lab findings:
• (+) food sensitivity testing
• altered cAMP/cGMP ratio
• (+) HLA-B27
• pustular lesions should be checked for candida

course and prognosis

• There is no conventional treatment that assures a cure, and the prognosis depends on the age of onset and the severity of presentation. Often, acute attacks can clear up, but it is rare for complete remissions to occur and last after conventional treatment.
• 6-7% of psoriatic patients develop psoriatic arthritis (usually following skin eruption); almost all such patients have nail involvement. Psoriatic arthritis is a rheumatoid-like arthritis with a (-) RF serology, although most patients have a (+) HLA-B27 antigen. The arthritis can be very severe and quickly cause major joint damage; treatment is similar to RA.

differential diagnosis

• seborrheic dermatitis: with scalp lesions (there is healthy skin between psoriatic lesions)
• squamous cell carcinoma in situ: with truncal lesions
• secondary syphilis: (+) blood serology
• fungal infections of nail: (+) fungal culture
• eczema
• lichen planus: has little scaling
• localized scratch dermatitis
• cutaneous LE
• tinea corporis: will have (+) fungal culture
• pityriasis rosea: "herald patch", has acute onset


footnotes