Psoriasis - Dermatology

Last updated 9.9.10 

Psoriasis 

Medical Student Core Curriculum 

in Dermatology 

Spring 2011

Module Instructions 

The following module contains a number 

of blue, underlined terms which are 

hyperlinked to the dermatology glossary, 

an illustrated interactive guide to clinical 

dermatology and dermatopathology. 

We encourage the learner to read all the 

hyperlinked information.

Goals and Objectives 

The purpose of this module is to help medical 

students develop a clinical approach to the 

evaluation and initial management of patients 

presenting with psoriasis. 

After completing this module, the medical 

student will be able to: 

• Identify and describe the morphology of psoriasis 

• Describe the clinical features of psoriatic arthritis 

• List the basic principles of treatment for psoriasis 

• Discuss the psychosocial impact of psoriasis 

• Develop an initial treatment plan, including patient 

education

Psoriasis: The Basics 

Psoriasis is a chronic multisystem disease with 

predominantly skin and joint manifestations 

Affects approximately 2% of the U.S. population 

Age of onset occurs in two peaks: ages 20-30 and 

ages 50-60, but can be seen at any age 

Waxes and wanes during a patient’s lifetime, is often 

modified by treatment initiation and cessation, and has 

few spontaneous remissions 

There is a strong genetic component 

• About 30% of patients with psoriasis have a first-degree 

relative with the disease

Classification of Psoriasis 

Classification is based on morphological descriptions 

The types of psoriasis are: 

• Plaque: scaly, erythematous patches, papules, and plaques that 

are often pruritic 

• Inverse: lesions are located in the skin folds 

• Erythrodermic: generalized erythema covering nearly the entire 

body surface area with varying degrees of scaling 

• Pustular: clinically apparent pustules 

• Rare, acute generalized variety called “von Zumbusch variant” 

• Palmoplantar – localized involving palms and soles 

• Guttate: presents with dew-drop lesions, 1-10mm salmon-pink 

papules with a fine scale 

Clinical findings in patients frequently overlap in more than 

one category 

Different types of psoriasis may require different treatment

A 

What Type of Psoriasis? 

C D 

B

Guttate Psoriasis 

Acute onset of raindropsized 

lesions on trunk 

and extremities in 

young adults, often 

preceded by 

streptococcal 

pharyngitis

Inverse Psoriasis 

Erythematous plaques 

in the axilla, groin, 

inframammary region, 

and other flexural areas. 

May lack scale due to 

moistness of area.

Pustular Psoriasis 

Characterized by psoriatic lesions with pustules. Often 

triggered by corticosteroid withdrawal. When 

generalized, pustular psoriasis can be a lifethreatening. 

These patients should be hospitalized and 

a dermatologist consulted.

Palmoplantar Psoriasis 

May occur as either plaque type or pustular type. 

Often very functionally disabling for the patient. 

The skin lesions of reactive arthritis typically occur 

on the palms and soles and are indistinguishable 

from this form of psoriasis.

Psoriatic Erythroderma 

Involves almost the entire 

skin surface; skin is bright 

red. Associated with fever, 

chills, and malaise. Like 

pustular psoriasis, 

hospitalization is sometimes 

required. 

* See module on 

erythroderma for more 

information

Question 

How would you describe these lesions? 

What type of psoriasis does this patient have?

Plaque Psoriasis 

Well-demarcated plaques with overlying silvery 

scale and underlying erythema 

• micaceous scale – peels in layers 

Chronic plaque psoriasis is typically symmetric and 

bilateral 

Plaques may exhibit: 

• Auspitz sign (bleeding after 

removal of scale) 

• Koebner phenomenon 

(lesions induced by trauma)

Plaque Psoriasis: The Basics 

PLAQUE PSORIASIS is the most common form, 

affecting 80-90% of patients 

Approximately 80% of patients with plaque 

psoriasis have mild to moderate disease – 

localized or scattered lesions covering less than 

5% of the body surface area (BSA) 

20% have moderate to severe disease affecting 

more than 5% of the BSA or affecting crucial 

body areas such as the hands, feet, face, or 

genitals

Psoriasis: Pathogenesis 

Psoriasis is a hyperproliferative state 

resulting in thick skin and excess scale 

Skin proliferation is caused by cytokines 

released by immune cells 

Systemic treatments of psoriasis target 

these cytokines and immune cells

Case One 

Mr. Ronald Gilson

Case One: History 

HPI: Mr. Gilson is a 24 year-old gentleman 

who presents with a red lesion around his 

belly button that has been present for one 

month with occasional itching. 

He has been reading on the internet and 

asks: “Do I have psoriasis?”

Case One, Question 1 

What elements in the history are 

important to ask when considering the 

diagnosis of psoriasis? 

a. Recent illnesses / Past medical history 

b. Medications 

c. Family history 

d. Social history 

e. All of the above

Case One, Question 1 

Answer: e 

What elements in the history are important to 

ask in this case to arrive at a diagnosis of 

psoriasis? 

a. Recent illnesses / Past medical history 

b. Medications 

c. Family history 

d. Social history 

e. All of the above

Ask About Past Medical History 

Psoriasis can be triggered by infections, especially 

streptococcal pharyngitis 

More severe in patients with HIV 

Up to 20% of psoriasis patients have psoriatic arthritis, 

which can lead to joint destruction 

There is a positive correlation between increased BMI and 

both prevalence and severity of psoriasis 

Patients with psoriasis may have an increased risk for 

cardiovascular disease and should be encouraged to 

address their modifiable cardiovascular risk factors 

Psoriasis has a serious impact on health-related quality of 

life (QOL)

Ask About Medication History 

Psoriasis can be triggered or exacerbated 

by a number of medications including: 

• Systemic corticosteroid withdrawal 

• Beta blockers 

• Lithium 

• Antimalarials 

• Interferons

Ask About Family History 

There is a strong genetic predisposition to 

developing psoriasis 

1/3 of psoriasis patients have a positive 

family history 

• However, this means up to 2/3 of patients 

with psoriasis do not have a family history 

of psoriasis, so a negative family history 

does not rule it out

Ask about Health-Related 

Behaviors 

Studies have revealed smoking as a risk 

factor for psoriasis 

Alcohol consumption is more prevalent in 

patients with psoriasis and it may increase 

the severity of psoriasis 

A higher BMI is associated with an increase 

prevalence and severity of psoriasis

Back to Case One 

Mr. Ronald Gilson 

Twenty-one year-old gentleman with 

red lesion around his umbilicus

Case One: History Continued 

PMH: no major illnesses or hospitalizations 

Medications: none 

Allergies: none 

Family history: adopted, does not know his 

family history 

Social history: lives with roommates in an 

apartment, graduate student in physics 

Health-related behaviors: no tobacco or drug 

use. Drinks 3-6 beers on weekends. 

ROS: negative

Psoriasis: Clinical Evaluation 

Although you should perform a full body 

skin exam, plaque psoriasis tends to 

appear in characteristic locations 

• Key Areas: scalp, ears, elbows and knees 

(extensor surfaces), umbilicus, gluteal cleft, 

nails, and sites of recent trauma 

• Observation of psoriatic lesions in these 

locations helps distinguish psoriasis from 

other papulosquamous (scaly) skin disorders

Back to Case One: Skin Exam 

Erythematous plaque 

with small amount of 

fine overlying scale 

around the umbilicus 


with overlying silvery 

scale is present in the 

gluteal cleft

DDx of Psoriasis 

Mr. Gilson is given a diagnosis of psoriasis 

based on the clinical evaluation 

Psoriasis is typically diagnosed on clinical exam 

because of its characteristic location and 

appearance 

Other conditions to be considered in the patient 

with chronic plaque psoriasis are: 

• Tinea corporis 

• Nummular eczema 

• Seborrheic dermatitis 

• Secondary syphilis 

• Drug eruption

Case Two 

Mr. Bruce Laney

Case Two: History 

HPI: Mr. Laney is a 68 yo gentleman with a history of 

psoriasis who presents with increased joint pain and 

joint changes. He currently uses a topical steroid to 

treat his psoriasis. 

PMH: psoriasis x 40yrs (difficult to control). 

Hypertension x 20 years, well-controlled with thiazide 

Medications: topical clobetasol for psoriasis, 

hydrochlorothiazide for blood pressure 


FH: mother and father both had psoriasis 

SH: lives with his wife in a house, retired, no children 

ROS: negative

Case Two: Skin Exam 

Large erythematous 

plaque with overlying 

silvery scale on 

anterior scalp 



scale at the external 

auditory meatus and 

behind the ear

Case Two: Exam Continued 

Extensor surface 

of the left arm has 

erythematous 

plaques with 

overlying silvery 

scale 

Also with vitiligo 

and macular 

depigmentation in 

the same region 

Nail pitting

Case Two: Exam Continued 

Erythematous and 

edematous foot, with 

dactylitis of the 2 nd digit, 

and destruction of the 

DIP joints 

Onychodystrophy

Case Two, Question 1 

Mr. Laney has psoriasis complicated by 

psoriatic arthritis. What part of his history 

or exam are most characteristic of a 

patient with psoriatic arthritis? 

a. history of extensive psoriasis 

b. presence of nail pitting 

c. use of clobetasol 

d. none of the above

Answer: b 

Case Two, Question 1 

Mr. Laney has psoriasis complicated by psoriatic 

arthritis. What part of his history/exam is most 

consistent with this diagnosis? 

a. history of extensive psoriasis 

b. presence of nail pitting (up to 90% of patients 

with psoriatic arthritis may have nail changes) 

c. use of clobetasol 

d. none of the above

Psoriatic Onychodystrophy 

Nail psoriasis can occur in all psoriasis subtypes 

Fingernails are involved in ~ 50% of all patients with 

psoriasis 

Toenails in 35% 

Changes include: 

• Pitting: punctate depressions of the nail 

plate surface 

• Onycholysis: separation of the nail 

plate from the nail bed 

• Subungual hyperkeratosis: abnormal 

keratinization of the distal nail bed 

• Trachyonychia: rough nails as if 

scraped with sandpaper longitudinally

Psoriatic Arthritis (PsA) 

Arthritis in the presence of psoriasis 

• A member of the seronegative spondyloarthropathies 

Symptoms can range from mild to severe 

Occurs in 10-25 percent of patients with psoriasis 

• Can occur at any age, but for most it appears between the ages 

of 30 and 50 years 

• It is NOT related to the severity of psoriasis 

Five clinical patterns of arthritis occur 

• Most common is oligoarthritis with swelling and tenosynovitis of 

one or a few hand joints 

Flares and remissions usually characterize the course of 

psoriatic arthritis

Psoriatic Arthritis Continued 

Health care providers are encouraged to actively 

seek signs and symptoms of PsA at each visit 

PsA may appear before the diagnosis of psoriasis 

If psoriatic arthritis is diagnosed, treatment should 

be initiated to: 

• Alleviate signs and symptoms of arthritis 

• Inhibit structural damage 

• Maximize quality of life 

Diagnosis is based on clinical judgment. 

• Specific patterns of joint inflammation, absence of 

rheumatoid factor, and the presence of skin and nail 

lesions of psoriasis aid clinicians in making the diagnosis of 

PsA

Psoriatic Arthritis 

Desquamation of the overlying 

skin as well as joint swelling and 

deformity (arthritis mutilans) of 

both feet 

Swelling of the PIP joints 

of the 2-4 th digits, DIP 

involvement of the 2 nd digit

Case Three 

Ms. Sonya Hagerty

Case Three: History 

HPI: Ms. Hagerty is an 18 year old healthy woman with a 

new diagnosis of psoriasis reports lesions localized to 

her knees with no other affected areas. She has not tried 

any therapy. 

PMH: none 

Medications: none 


Family history: non-remarkable 

Social history: lives in the city with her parents and 

attends high school 

Health-related behaviors: 

ROS: slight pruritus

Case Three: Skin Exam 

Erythematous plaques 


scale on the extensor 

surface of the knee.

Case Three, Question 1 

Which of the following would you recommend 

to start treatment for Ms Hagerty’s psoriasis? 

a. systemic steroids 

b. immunomodulators 

c. high potency topical steroid 

d. low potency topical steroid 

e. all of the above

Answer: c 


Which of the following would you recommend to 

start treatment for Ms Hagerty’s psoriasis? 

a. systemic steroids 

b. biologic 

c. high potency topical steroid 

d. low potency topical steroid 

e. Topical clotrimazole

Psoriasis: Treatment 

Since the psoriasis is localized (less than 

5% body surface area), topical treatment 

is appropriate 

First line agents: High potency topical 

steroid in combination with calcipotriene 

(vitamin D analog) 

Other topical options: tazarotene, salicylic 

or lactic acid, tar, calcineurin inhibitors

Psoriasis: Treatment 

Factors that influence type of treatment: 

• Age 

• Type of psoriasis: 

• plaque, guttate, pustular, erythrodermic psoriasis 

• Site and extent of psoriasis: 

• localized = 30% involvement 

• Previous treatment 

• Other medical conditions 

Patients with localized plaque psoriasis can be managed by 

a primary care provider 

Psoriasis of all other types should be evaluated by a 

dermatologist

Psoriasis: Topical Treatment 

Medication Uses in Psoriasis Side Effects 

Topical steroids Plaque-type psoriasis Skin atrophy, 

hypopigmentation, striae 

Calcipotriene 

(Vitamin D derivative) 

Tazarotene 

(Topical retinoid) 

Salicylic or Lactic acid 

(Keratolytic agents) 

Use in combination with topical 

steroids for added benefit 

Plaque-type psoriasis. Best when 

used with topical corticosteroids. 

Plaque-type psoriasis to reduce 

scaling and soften plaques 

Skin irritation, photosensitivity 

(but no contraindication with 

UVB phototherapy) 

Skin irritation, photosensitivity 

Systemic absorption can occur 

if applied to > 20% BSA. 

Decreases efficacy of UVB 

phototherapy 

Coal tar Plaque-type psoriasis Skin irritation, odor, staining of 

clothes 

Calcineurin inhibitors Off-label use for facial and 

intertriginous psoriasis 

Skin burning and itching

Estimating BSA via Palm of Hand 

1 Palm = 1% 

BSA

Estimating topicals: 

Fingertip unit 

Quantity of topical 

medication placed on 

pad of finger from distal 

tip to DIP joint 

Fingertip unit = 500 mg 

= treats 2% BSA

Estimating Topical Therapy 

Amounts 

2% BSA = 500mg = 0.5g 

• 2% BSA bid x 1 month = 0.5 g x 2 x 30 = 30 g 

• 5% BSA bid x 1 month = 1.25 g x 2 x 30 = 75 g 

Can also use the “Rule of 15” 

%BSA x 15 = grams needed to treat bid x 1 month 

• 10% BSA bid x 1 month = 150 g 

• 100% BSA bid x 1 month = 1500 g


Which of the following 

prescriptions would you give 

Ms Hagerty? 

a. Clobetasol 0.05% ointment, 

applied BID 

b. Tacrolimus 0.1% ointment, 

applied BID 

c. Coal tar solution 10%, applied 

at bedtime 

d. Etanercept 50mg, 

subcutaneous, twice per week

Answer: a 


Which of the following 

prescriptions would you use 

for Ms Hagerty? 

a. Clobetasol 0.05% ointment, 

applied BID 

b. Tacrolimus 0.1% ointment, 

applied BID 

c. Coal tar solution 10%, applied 

at bedtime 

d. Etanercept 50mg, 

subcutaneous, twice per week


Which of the following prescriptions is 

correct for topical clobetasol 0.05% 

ointment for a 3 month supply? 

a. Clobetasol 0.05%, apply twice a day to the affected 

areas, dispense 30 grams 

b. Clobetasol 0.05%, apply twice day to the affected areas, 

dispense 3 grams 

c. Clobetasol 0.05%, apply twice a day to the affected 

areas, dispense 90 grams 

d. Clobetasol 0.05%, apply twice a day to the affected 

areas, dispense 9 grams


Answer: c 

Which of the following prescriptions is correct for 

topical clobetasol 0.05% ointment for a 3 month 

supply? 

a. Clobetasol 0.05%, apply twice a day to the affected areas, 


b. Clobetasol 0.05%, apply twice day to the affected areas, 


c. Clobetasol 0.05%, apply twice a day to the affected areas, 

dispense 90 grams (2% BSA x 15 = 30 grams/month x 3 months 

= 90 grams) 

d. Clobetasol 0.05%, apply twice a day to the affected areas, 

dispense 9 grams

Clinical Pearl 

Topical medications for psoriasis are more 

effective when used with occlusion which 

allows for better penetration 

A bandage, saran-wrap, gloves, or socks 

placed over the medication can serve this 

purpose


What would be an appropriate 

treatment if a patient had 

presented with this skin 

exam? 

a. systemic steroid 

b. topical steroid 

c. topical steroid and systemic 

steroid 

d. topical steroid and UV light 

therapy 

e. all of the above


Answer: d 

What would be an appropriate 

treatment if a patient had 

presented with this skin exam? 

a. systemic steroid 

b. topical steroid 

c. topical steroid and systemic 

steroid 

d. topical steroid and UV light 

therapy 

e. all of the above

Psoriasis: System Treatment 

In patients with moderate to severe disease, 

systemic treatment can be considered and 

should be supplemented with topical treatment 

Many patients with moderate to severe psoriasis 

are only given topical therapy and experience 

little treatment success 

• Undertreating the patient can lead to a loss of hope 

regarding their disease 

Oral steroids should never be used in psoriasis 

as they can severely flare psoriasis upon 

discontinuation

Systemic Treatment 

There are 3 choices for systemic treatment: 

1. Phototherapy: narrow-band ultraviolet B light (nbUVB), 

broad-band ultraviolet B light (bbUVB), or psoralen plus 

ultraviolet A light (PUVA) 

2. Oral medications: methotrexate, acitretin, cyclosporine 

3. Biologic Agents: T- cell blocker (alefacept), TNF-α 

inhibitors (infliximab, etanercept, adalumimab), IL 12/23 

blocker (ustekinumab) 

The choice of systemic therapy depends on multiple 

factors: convenience, side effect risk profile, presence or 

absence of psoriatic arthritis (PsA), co-morbidities 

Systemic treatment for psoriasis should be given only 

after consultation with a dermatologist

The Patient’s Experience 

A successful treatment regimen should include 

patient education as well as provider awareness of 

the patient’s experience 

• Find out the patients’ views about their disease 

• Ask the patient how psoriasis affects their daily living 

• Ask about symptoms such as pain, itching, burning, 

and dry skin 

• Ask patients about their experience with previous 

treatments 

• Important to ask patients about their hopes and 

expectations for treatment 

• Provide time for patients to ask questions

Psoriasis and QOL 

Psoriasis is a lifelong disease and can affect all 

aspects of a patient’s QOL (even in patients with 

limited skin involvement) 

Remember to address both the physical and 

psychosocial aspects of psoriasis 

Many patients with psoriasis: 

• Feel socially stigmatized 

• Have high stress levels 

• Are physically limited by their disease 

• Have higher incidences of depression and alcoholism 

• Struggle with their employment status

Take Home Points 

Psoriasis is a chronic multisystem disease with predominantly skin 

and joint manifestations 

About 1/3 of patients with psoriasis have a 1 st -degree relative with 

psoriasis 

Different types of psoriasis are based on morphology: plaque, 

guttate, inverse, pustular, and erythrodermic 

Plaque psoriasis is the most common, affecting 80-90% of patients 

A detailed history should be taken in patients with psoriasis 

Plaque psoriasis is often diagnosed clinically 

Nail disease is common in patients with psoriasis 

Psoriatic arthritis is a member of the seronegative 

spondyloarthropathies

Take Home Points 

Health care providers are encouraged to actively seek signs and 

symptoms of psoriatic arthritis at each visit 

Topical treatment alone is used when the psoriasis is localized 

Topical medications for psoriasis are more effective when used with 

occlusion, which allows for better penetration 

Patients with moderate to severe disease often require systemic 

treatment in addition to topical therapy 

Oral steroids should never be used in psoriasis 

Systemic treatment includes phototherapy, oral medications and biologic 

agents. 

A succesful treatment plan should include patient education as well as 

provider awareness of the patient’s experience 

Psoriasis is a lifelong disease and can affect all aspects of a patient’s 

quality of life

End of the Module 

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Psoriasis - Dermatology

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