Psoriasis

Question 1

Psoriasis definition?

Answer 1

Relapsing-remitting inflammatory skin disease characterized by well-defined plaques bearing adherent silvery scales

Question 2

What are the two main abnormalities underlying psoriasis?

Answer 2

Hyperproliferation of keratinocytes

Inflammatory cell infiltrate dominated by neutrophils, TNF and T lymphocytes

Question 3

Features of inheritance of psoriasis? (3)

Answer 3

Probably polygenic; 70% concordance in MZ twins compared to 20% DZ; more likely to inherit from father than mother

Question 4

Strongest genetic linkage for inheritance of psoriasis?

Answer 4

PSOR1 accounts for up to 50% of genetic susceptibility, located within the MHC Class I locus

Question 5

How does psoriasis differ from the ichthyoses?

Answer 5

Accumulation of inflammatory cells in psoriasis

Question 6

Precipitants of psoriasis onset/flare? (7)

Answer 6

Trauma (Koebner phenomenon)
Infection- tonsillitis caused by strep pyogenes –> guttate psoriasis
Hormonal- hypocalcaemia caused by hypoparathyroidism is a rare precipitant. Tends to remit during pregnancy and flare post-partum
Sunlight- tends to make better but makes worse in 10%
Drugs- steroid rebound
Smoking
Emotional stress

Question 7

Histological changes in psoriasis (5)

Answer 7

Parakeratosis (peristence of nuclei in the stratum corneum)
Irregular thickening of the epidermis
Epidermal PML infiltrates and microabscesses
Dilated and tortuous capillary loops in the dermal papillae
T-lymphocyte infiltrate in the upper dermis

Question 8

Commonest patterns of psoriasis?

Answer 8

Plaque pattern

Guttate pattern

Question 9

What is guttate psoriasis often triggered by?

Answer 9

Strep throat in children

Question 10

Which sites does psoriasis favour?

Answer 10

The extensor surfaces of knees and elbows

Question 11

Nail involvement in psoriasis (3)

Answer 11

Pitting
Oncholysis
Subungual hyperkeratosis

Question 12

Less common patterns of psorasis

Answer 12

Napkin psoriasis in a baby- increases risk of ordinary psoriasis later in life
Generalized pustular psoriasis
Erythrodermic psoriasis

Question 13

Skin becomes universally and uniformly red with variable scaling

Answer 13

Erythrodermic psoriasis

Question 14

Triggers for erythrodermic psoriasis (3)

Answer 14

Irritant effect of tar or dithranol
Drug eruption
Withdrawal of potent steroids

Question 15

What tools are available to assess the effect of psoriasis on the patient’s quality of life?

Answer 15

Dermatology quality of life index (DLQI)

Psoriasis Area and Severity Index (PASI)

Question 16

What are the main LOCAL options for management of psoriasis? (8)

Answer 16

Vitamin D analogues such as calcipotriol, calcitriol
Topical steroids
Local retinoids
Dithranol
Coal tar preparations
Salicylic acid
Calcineurin inhibitors
UV radiation

Question 17

Which treatment is the longterm mainstay of psoriasis therapy, and why do patients like it?

Answer 17

Vitamin D analogues- odourless, colourless and do not stain

Question 18

What is the main adverse effect of Vit D analogues?

Answer 18

Transient local irritation- for this reason may not suit treatment of the face

Question 19

What is the best practice regarding the use of steroids for psoriasis?

Answer 19

Short intermittent use for flares, and don’t use for generalised psoriasis

Question 20

Problems of steroid use in psoriasis (4)

Answer 20

Dermal atrophy
Tachyphylaxis
Precipitation of unstable psoriasis
Rarely- adrenal suppression due to absorption in extensive cases

Question 21

What is the broad mechanism of dithranol and coal tar preparations?

Answer 21

Inhibition of DNA synthesis

Question 22

Narrowband UVB uses light at what wavelength?

Answer 22

311nm

Question 23

What are the risks of UVB treatment? (2)

Answer 23

Acute phototoxicity (sunburn-like reaction)
Long term photodamage and skin cancer

Question 24

Management of scalp psoriasis? (2)

Answer 24

Oils containing salicylic acid

Coal tar shampoos

Question 25

Management of guttate psoriasis?

Answer 25

Systemic antibiotic (penicillin V)
Emollients, topical tar, phototherapy

Question 26

Systemic treatments for psoriasis

Answer 26

PUVA
Retinoids (+/- PUVA)
Methrotrexate
Ciclosporin
Biologics e.g. etanercept, infliximab

Question 27

What needs to be monitored when patients are commenced on retinoids?

Answer 27

LFTs and lipids
Mental state
FBCs, U&Es

Question 28

What is the main drawback of dithranol?

Answer 28

Burns normal skin and stains clothing/bedding purple

Question 29

What is the mechanism of methotrexate?

Answer 29

Inhibition of dihydrofolate reductase, inhibiting purine biosynthesis and therefore lymphoid proliferation

Question 30

Main adverse effects of methotrexate? (4)

Answer 30

Risk of hepatic fibrosis
Bone marrow suppression
Teratogenicity- shouldn’t be given to women of childbearing age
Oligospermia

Question 31

Complications of psoriasis (3)

Answer 31

Psoriatic arthropathy (5-10%)
Increased risk of cardiovascular disease
Increased prevalence of metabolic syndrome

Question 32

Main patterns of joint involvement in psoriasis? (5)

Answer 32

Assymmetric oligoarthritis (60-70%)
Symmetrical polyarthritis
DIP joint disease
Arthritis mutilans
Axial arthritis

Question 33

Differential diagnoses to consider in psoriasis (5)

Answer 33

Discoid eczema
Seborrhoeic eczema
Pityriasis rosea (may be confused with guttate)
Secondary syphilis
Cutaneous T cell lymphoma
Tinea unguium (may be confused with nail changes)