Psoriasis

Question 1

definition

Answer 1

chronic skin condition characterised by scaly erythematous plaques, typically relapsing and remitting

Question 2

pathogenesis

Answer 2

the epidermis in the plaques is hyperproliferative
proliferation and dilatation of blood vessels in the epidermis + infiltration of inflammatory cells (T cells +/- neutrophils)
plaque psoriasis the most common form (~90%)
if both parents affected, risk to offspring is ~50%
NB 60% of patients will also be depressed

Question 3

triggers

Answer 3

stress
infections
skin trauma (Koebner phenomenon), drugs, alcohol, obesity, smoking, climate

Question 4

Koebner phenomenon

Answer 4

the development of psoriasis in an area of skin following trauma, where psoriasis had not been seen previously (Koebnerisation)

Question 5

chronic plaque psoriasis

Answer 5

symmetrical well defined red plaques with silvery scales

extensor surfaces of knees, elbows, scalp and sacrum

Question 6

flexural psoriasis

Answer 6

plaques in moist flexural areas (axilla, groins, submammary and umbilicus)
often less scaly and misdiagnosed as fungal infections

Question 7

guttate psoriasis

Answer 7

large numbers of small plaques (<1cm) over the trunk and limbs are seen in the young
especially after strep infections
usually lasting 3-4 months

Question 8

pustular psoriasis

Answer 8

yellow/brown pustules with plaques affecting the palms and soles (M:F, 9:1)

Question 9

generalised (erythrodermic) psoriasis

and generalised pustular psoriasis

Answer 9

may cause severe systemic upset (fever, increased WCC, dehydration)
medical emergencies requiring urgent hospital referral
NB also triggered by rapid withdrawal of steroids

Question 10

nail changes

Answer 10

in 50% of cases
pitting
onycholysis (separation from the nail bed)
thickening and subungual hyperkeratosis

Question 11

psoriatic arthropathy

Answer 11

7% develop seronegative arthropathy (no rheumatoid factor)
5 types:
1. monoarthritis or oligomonoarthritis
2. psoriatic spondylitis
3. asymmetrical polyarthritis
4. arthritis multilans (destructive) (can lead to telescoping when occurring in fingers
5. rheumatoid-like polyarthritis

Rx: NSAIDs, DMARDs (eg methotrexate) and anti-TNF agents (eg infliximab ?)

Question 12

management

Answer 12

education is vital
control not cure
find out what the patient finds the most distressing
consider phototherapy or systemic therapy if >10% of body surface affected
emollients reduce scale and help relieve irritation

Question 13

topical Tx

Answer 13

plaque psoriasis: use a topical corticosteroid (eg betnovate) once a day, + a topical vit D preparation (eg dovonex) which affects cell division, once a day
do not use potent corticosteroids for more than 8 weeks, and have a treatment break of 4 weeks before restarting

Question 14

phototherapy

Answer 14

most useful in uncontrolled guttate or plaque psoriasis or when the disease is widespread (+/- topical adjunctive or systemic treatment)

PUVA (psoralen + UVA) is suitable for extensive large plaque psoriasis (oral psoralen) or pustular psoriasis (topical psoralen)
there is increased risk of skin Ca, especially SCC

Question 15

non-biologic oral drugs

Answer 15

for severe psoriasis
methotrexate 10-20mg/week PO
most useful in elderly patients, or psoriatic arthropathy
avoid in young due to long term risk of hepatic fibrosis
monitor FBC and LFT

Question 16

biological drugs

Answer 16

inhibit T-cell activation and function, or neutralise cytokines
consider infliximab, adalimumab, etanercept (TNF antagonists) or if these have failed, ustekinumab (interleukin inhibitor)
all are for specialist use only