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Papulosquamous Conditions


Psoriasis: A hereditary, proliferative, inflammatory disorder of the skin manifested by red papules and chronic scaling plaques. Pustules occur in a characteristic distribution. May include an inflammatory arthritis.

Pityriasis rosea: A common inflammatory skin disease resembling a acute viral exanthem of unknown etiology. Scaling occurs in a typical pattern



Psoriasis: Scaly, red, sometimes pruritic thick patches, primarily on the skin of the elbows, knees, scalp, or trunk. May occur as red, Pruritic, scaly skin, or slightly tender pruritic pustules of palms or soles or as chronic red dots on trunk. May have mild to disabling arthritis.

Pityriasis rosea: Large scaly patch usually on the trunk which precedes spreading lesions of dull redish pink or tawny color on body centrally, spreading peripherally onto extremities. Asymptomatic to significant pruritis.


Psoriasis: Usually adults, but up to 30 percent may be less than 20-years-old, especially females. Overall incidence is the same in males and females. Rare in children.

Pityriasis rosea: Seventy-five percent occur 10-to35-year age group.


Psoriasis: Acute in small dot trunk guttate form, pustular, local, and generalized forms. Chronic in plaque forms.

Pityriasis rosea: Acute with enlarging maculopapule.


Psoriasis: Usually months, but weeks sometimes in acute onset types.

Pityriasis rosea: Three to 10 weeks with an occasional several month case.


Psoriasis: Small single lesions or groups that occur locally in one area (e.g., genitalia, axillae) to regional lesion or groups (scalp), or generalized or universal (all of skin, nails).

Pityriasis rosea: A few lesions to innumerable.

Aggravating Factors

Psoriasis: Minor trauma, pressure points, systemic corticosteroids, lithium, alcohol, chloroquine, intense sunlight, stress, obesity.

Pityriasis rosea: Ampicillin, heat.

Alleviating Factors

Psoriasis: Mild to moderate sun exposure, topical corticosteroids, stress management, hydration, lubrication, antipruritics.

Pityriasis rosea: Sunlight, antipruritics if indicated.

Associated Factors

psoriasis: Genetics, beta hemolytic streptococcal infection.

Pityriasis rosea: Winter season higher incidence, mild leukopenic lymphocytosis disease peak.

Physical Examination


Psoriasis: Asymmetric, but bilateral salmon red papules and plaques, with sharp margins and silver/white scale, inflamed pustules or erythrodermic, diffuse, general peely red lesions without sharp border.

Lesions may be round, oval, polycyclic, or annular in discrete single lesion pattern. May also occur in confluent large patches, serpiginous or arciform, localized, regionalized, or general as in erythrodermic entire skin form. Nails may have pits, ridges, onycholysis, or pathognomonic yellowish spots under the nail plate. Twenty five percent of patients have nail involvement. Alopecia is not common even with the thickest of plaques. Inflammatory arthritis most common in pustular and erythrodermic psoriasis and may involve hands, feet, or joints. May cause mutilating bone erosion, osteolysis, and ankylosis involving the sacroiliac, hip, and cervical areas. Plaques most prevalent over extensor pressure surfaces. Guttate papules are worse on the trunk. Pustular forms are mostly on the extremities and rarely generalized. Intertrigenous areas may be affected, but without thick plaques and finer scaling.

Pityriasis rosea: A herald patch precedes more general eruption by 3 days to a couple of weeks. In 80 percent of patients this patch is the largest lesion of the exanthem. The lesions are fawn salmon to bright red in color, are maculopapular and usually have a collarette of fine scales at the margins. Lesions are typically ovoid in shape and are distributed in cleavage lines, like a dermatomal pattern (characteristic Christmas tree appearance) on the back. The exanthem is usually confined to the trunk and proximal extremities.


Psoriasis: Probably has a multi factorial pathogenesis, thus the varied presentations and systemic involvement. Epidermal cell turnover time is decreased, likely due to shorter cell cycle and increased cells in the dividing pool. Changes occur in keratogenous epidermal zone and in dermis with inflammation. Epidermal proteinases are elevated and also playa role. Neutrophils, lymphocytes, and monocytes are mobilized which form microabscesses of ;munro in the stratum corneum.

Pityriasis rosea: Specific etiology is unproven but still most widely believed to be viral. The immune system probably plays some role as well. Histopathologic changes are nonspecific, but include mild acanthosis, parakeratosis, perivascular lymphohistiocytic infiltrate, and red cell extravasation.

Diagnostic Studies


Psoriasis: None needed when characteristic clinical features are present.

Pityriasis rosea: None except to rule out conditions in the differential.

Radiology: Not applicable.


Psoriasis: Biopsy may be helpful and suggestive but not necessarily specific. Histology changes overtime with acute onsets to chronic forms.

Differential Diagnosis


Psoriasis: Skin injuries from trauma or infection: Commonly develop a psoriasis called Koebner's phenomena. Be alert to slight changes and persistent white scaling on red papules and plaques in broken skin sites from any cause.

Pityriasis rosea: Not applicable.


Psoriasis: Candidiasis: Mimics intertriginous psoriasis, but is KOH positive and won't clear with psoriasis treatment, may even flare.

Pityriasis rosea: Fungal cause: Will be positive on KOH and culture.

Secondary syphilis: Positive serology.


Psoriasis: Glucagnoma syndrome: A malignant pancreatic islet cell tumor that has atypical psoriasiform lesions with vesicles and erosions. Includes lesions in groin and face and marked weight loss; anemia with histology distinguish it.

Psoriasiform drug eruption: Positive history for first-time use of beta blockers, gold, or methyldopa. Clear easily with drug withdrawal and treatment.

Pityriasis rosea: Not applicable.


Psoriasis: Mycosis fungoides: Mimics psoriasis, but resistant to treatment and generally less thick plaques and less silver, white scale.

Pityriasis rosea: Not applicable.

Vascular: Not applicable.

Congenital:Not applicable.


Psoriasis: Seborrheic dermatitis: May be indistinguishable in certain sites and morphology. Usually yellower scale, especially of scalp. Responds to same treatments.

Lichen simplex chronicus: May complicate psoriasis due to pruritis and itch rub. Responds to same treatments.

Pityriasis rosea: Drug eruption: Can usually be elicited by history. Guttate psoriasis: Not only a collarette scale but may have scale over entire surface.



Lubrication and desquamation: Initial and daily treatment with ointment or cream based emollients containing 1 to 2 percent salicyclic acid or 5 to 10 percent lactic acid or 10 to 20 percent urea.

Crude coal tar preparations for topical use are effective and have been used since the nineteenth century. Limited by tendency to irritate and stain. Newer forms are less messy. Anthrallin creams are traditionally helpful, now with 30-minute contact time and increasing strengths over weeks of therapy. Effective but time consuming and troublesome.

Corticosteroids are the most widely used treatment but can cause side-effects and can be expensive. Available in a wide range of potencies and absorbencies. The most potent (e.g., clobetasol, betamethasone diproprionate) should be reserved for thickest plaques in relatively small regions and not be used on face or intertriginous areas.

Middle potencies should be used for large areas in less severe conditions and short term in the worst intertriginous areas. Be alert to the risk of treating entire skin areas (e.g., erythroderrnic-cortisol suppression, glucose intolerance, rarely Cushing syndrome). Risk increases with occlusion, potent drug use, in children or the liver impaired.

UVB and UVA wave exposure can be quite effective with serial exposures. UVB wave effect is enhanced after tar application (Goeckerman therapy). UVA is enhanced with 8-methoxypsoralen topically or orally which becomes modem PUVA. Very effective but protective

eyewear is required 8 to 12 hours after medicating orally. Systemic therapy should only be used when the risk of side-effects is weighed against the benefits in long term treatment. The response can be very helpful and dramatic in extensive involvement such as pustular or erythrodermic psoriasis. These should probably only be used by specialists familiar with their use, toxicity, side-effects, and drug interactions.

Other treatments include Methotrexate 10 to 20 mg divided into 3 doses and given 12 hours apart, weekly. Oral and intramuscular forms available. Side effects include nausea, gastrointestinal upset, hepatotoxicity, and bone marrow suppression. There is a lifetime dose limit depending on liver.

Etretinate (a Retinoid): Has individualized doses of 10 to 25 mg, 1 to 3 times daily with gradual titration and adjustments to lowest effective dose. Side-effects include hypervitaminosis A syndrome, affects skin, mucous membranes, and the musculoskeletal system, elevates serum lipid levels, is hepatotoxic, teratogenic, and embryotoxic.

Cyclosporin: In lower doses than those used for organ transplantation helps significantly until discontinued. Psoriasis tends to return, but not in the rebound fashion seen with systemic corticosteroids. Side effects include nephrotoxicity, hypertension, hepatotoxicity, neurologic abnormalities, and an increased incidence of lymphoma. Treatment combinations are commonly used and specifically tailored to the individual.

Pityriasis rosea: Sunlight or DVB exposure helps control if pruritis is present and may hasten lesion involution. Oral antihistamines and topical corticosteroids are also helpful if pruritis is a problem.

Pediatric Considerations

Psoriasis: One-third of individuals affected by psoriasis will present within the first two decades. Psoriasis is rare in the newborn. Preferred sites include scalp, knees, elbows, umbilicus, and genital area. Guttate psoriasis is a form of psoriasis seen predominately in children. The onset frequently follows a recent streptococcal pharyngitis by 2 or 3 weeks. The lesions may mimic a viral exanthem. Treatment varies with age, type, site, and extent of the disease. Tar preparations (enhanced by UV light) are useful. Topical corticosteroids are extremely effective but must be used with caution. Systemic steroids are typically contraindicated in childhood psoriasis. The safety of PUVA therapy has not yet been established for children. Psoriasis in infants and acute guttate psoriasis should be managed conservatively.

Pityriasis rosea: Pityriasis rosea is most commonly seen in adolescents and children. It may be preceded by a prod rome of pharyngitis, fever, malaise, but rarely do children report such symptoms. An annular, scaly,erythematous lesion, (the herald patch), precedes the generalized eruption in approximately 80 percent of children. Treatment may be unnecessary. After the eruption has resolved, post inflammatory hypo pigmentation or hyper pigmentation may be evident, particularly in black patients.

Obstetrical Considerations

Potent topical steroids should be avoided when treating psoriasis. They should be used only when the benefit to the mother clearly justifies the risk to the fetus. If used, this group of topical steroids should not be applied over extensive areas, in large amounts, or for prolonged periods.

Etrentinate, a retinoid, is absolutely contraindicated during pregnancy due to teratogenic and embryotoxic effects. It is sometimes used for the treatment of the pustular and erythrodermic forms of psoriasis. Avoidance of pregnancy while taking this drug is mandatory.

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   Lupus Erythematosus
   Lyme Borreliosis
   Lymphogranuloma Venereum
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   Metastatic Cancer to the Skin
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   Necrobiosis Lipoidica
   Neisseria Gonorrhoeae Infections
   Nodular Melanoma
   Nodular Vasculitis
   Nongenital Herpes Simplex Virus Infection
   North American Blastomycosis
   Oral Hairy Leukoplakia
   Oropharyngeal Candidiasis
   Other Viral Infections
   Papulosquamous Conditions
   Pediculosis Capitis
   Pediculosis Pubis
   Photoallergic Drug Induced Photosensitivity
   Phototoxic Drug Induced Photosensitivity
   Pitted Keratolysis
   Pityriasis Versicolor
   Polyarteritis Nodosa
   Polymorphous Light Eruption
   Porphyria Cutanea Tarda
   Port-Wine Stain
   Premalignant and Malignant Skin Tumors
   Pressure Ulcers
   Pruritic Urticarial Papules
   Pseudoxanthoma Elasticum
   Pyogenic Granuloma
   Radiation Dermatitis
   Raynaud's Disease
   Reiter's Syndrome
   Rocky Mountain Spotted Fevers
   X-Linked Hyper-IgM Syndrome
   Xeroderma Pigmentosum
   Yellow Fever
   Yellow Nail Syndrome
   Zinc Deficiency

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