Evaluation/Diagnostic Protocol


History: Where—scalp, knees, elbows, lower back, nails, fingers, spine, trunk, axilla and intergluteal folds?; How long—days, weeks, months, years?; Symptoms—pruritic, painful, bleeding?;  Quality—red, puffy, pink, erythematous plaque with silvery white scales?;  Severity—good/bad day?;  Mod. Factors—previous treatment?; Context—associations?;  Timing—when does it occur? Any constitutional &/or arthritis symptoms?  Family history?

Objective: Thorough skin exam.  Look for sharply demarcated erythematous plaques with silvery white scales. Lesions can involve scalp, elbows, knees, nails, hands, feet, trunk, and intergluteal fold. 

Chronic Plaque Psoriasis:  most common.  Sharply demarcated, erythematous papulosquamous lesions. Less often over 90% of BSA involved or numerous small widely disseminated papules and plaques are seen (guttate psoriasis).  Skin lesions have: erythema, thickening, and scale.  Size of lesion may vary from pinpoint papule to over 20cm in diameter; outline of lesion is usually circular, oval or polycyclic (derived from several smaller units) and sometimes surrounded by a pale blanching ring (Woronoff’s ring).  During exacerbations, lesions often itch.

Guttate Psoriasis: common form of the disease in children. Small, discrete papules and plaques. Prognosis in children excellent with spontaneous remissions in weeks to months; adults can become chronic.

Erythrodermic Psoriasis:  variant of psoriasis characterized by generalized erythema and scaling and its onset can be gradual or acute.  Clues to diagnosis include previous plaques in classic locations, characteristic nail changes and facial sparing.

Generalized Pustular Psoriasis:  an unusual manifestation of psoriasis and triggering factors include pregnancy, tapering of corticosteroid, hypocalcemia, infections and in case of localized disease, topical irritants. 

·         Zumbush pattern:  generalized eruption starts abruptly with erythema and pustulation. Skin is painful during this phase and patient has fever and feels ill.  After several days, the pustules resolve and extensive scaling is observed. 

·         Annular Pattern:  characterized by annular lesions, consisting of erythema and scaling with pustulation at the advancing edge.  Lesions enlarge by centrifugal expansion over a period of hours to days, healing occurs centrally. General malaise, localized tenderness and fever may occur. 

·         Exanthematic type:  acute eruption of small pustules, abruptly appearing and disappearing in a few days.  Usually follows an infection or may occur as a result of administration of specific medications (lithium).  Systemic symptoms do not usually occur.  Overlap between this form of pustular psoriasis and pustular drug eruptions, also referred to as acute generalized exanthematous pustulosis.

·         Localized pattern:  Sometimes pustules appear within or at the edge of existing psoriatic plaques.  This can be seen during the unstable phase of chronic plaque psoriasis and following the application of irritants i.e., tars.


Lab: CBC, chemistry panel, sed rate, RPR, RF; consider biopsy. 


Differential Diagnosis

Plaque Psoriasis

  1. SCC: if there is a single or limited number or erythematous plaques, especially if they are treatment resistant, the possibility of SCC needs to be excluded via histologic examination.
  2. Seborrheic dermatitis: cannot co-exist with psoriasis.  
  3. hypertrophic lichen planus vs plaque psoriasis: when psoriasis involves the shins, they may be confused with characteristic violaceous lesions elsewhere and mucosal involvement usually points to correct diagnosis
  4. Sezary syndrome-rare disease; defined by triad of erythroderma, generalized lymphadenopathy, and presence of neoplastic T cells in skin, lymph nodes and peripheral blood. Erythroderma may be associated with marked exfoliation, edema, and lichenification; it is intensely pruritic.  Lymphadenopathy, alopecia, onychodystrophy and palmoplantar hyperkeratosis are common.  Clinical picture may be preceded by non-diagnostic dermatitis.  Poor prognosis.
  5. Pityriasis rubra pilaris--
  6. drug reactions


Guttate Psoriasis

  1. Small plaque para psoriasis—patches that are less than 5 cm in diameter; generally asymptomatic, lesions are chronic and may wax and wane early in their clinical course, but become persistent and can progress to more extensive. Round oval patches that are variable erythematous but less intense than psoriasis and covered with fine scale. +digitate dermatosis: presents as elongated finger like patches symmetrically distributed on the flanks. 
  2. Pityriasis lichenoides chronica—scaly lesions; papules are erythematous to red brown and scaly; regresses over weeks to months. Lesions often subside leaving hypopigmented macules that may be presenting complaint in darker skinned persons.  Can resolve spontaneously after weeks to months or may have a chronic relapsing course. 
  3. Secondary syphilis—secondary stage of disease results from hematogenous and lymphatic dissemination of treponemes after few weeks or months (4-10 weeks).  Characterized by recurrent activity of the disease with mucocutaneous as well as systemic manifestations; prodromal symptoms included low grade fever, malaise, sore throat, adenopathy, weight loss, muscle aches, and headache. 
  4. Pityriasis rosea—individual lesions usually oval in shape and their long axis is oriented along lines of cleavage; a solitary lesion appears on trunk (less often on neck) and enlarges during the ensuing days. It predates the eruption by hours to days; patch is skin-pink-salmon colored patch or plaque with a slightly raised advancing margin. It size is 2-4cm but can be as small as 1cm or large as 10cm.  Center shows a characteristic small fine scales and the margin has a larger more obvious trailing collarette of scale with free edge pointing inwards.  Some patients may have headache, fever, arthralgias, or general malaise.  Face, palms, and soles are usually spared.  Usually persists for 6-8 weeks and then spontaneously resolves but can last over 5 months. + Pruritus.
  • Lesions of guttate psoriasis rarely involve the palms or soles and are often more erythematous than those of para psoriasis. 
  • When there is more limited number of lesions, the possibility of tinea corporis is raised and when the upper trunk is the predominant site of involvement, pemphigus foliaceus.