Skin Pathology

Question 1

Define hyperkeratosis

Answer 1

Thickening of the stratum corneum, leading to increased keratin

Question 2

Define acanthosis

Answer 2

Thickening of stratum spinosum

Question 3

Define spongiosis

Answer 3

Intercellular oedema

Question 4

Define lentiginous

Answer 4

Linear pattern of melanocyte proliferation within the epidermal basal cell layer. Can be reactive or neoplastic

Question 5

Describe the histological appearance of acute dermatitis

Answer 5

Spongiosis, inflammatory infiltrate in dermis, dilated dermal capillaries

Question 6

Describe the histological appearance of chronic dermatitis

Answer 6

Acanthosis, crusting, scaling

Question 7

Describe the clinical features of atopic dermatitis

Answer 7

Inflamed, dry itchy rash on face and scalp of infants or flexural surfaces of children

Question 8

Describe the clinical features of contact dermatitis

Answer 8

Erythema, swelling, and pruritic rash as a type IV hypersensitivity reaction, commonly to nickel or rubber. Commonly affects ear lobes, neck (jewellery), wrist (watch strap), and feet (shoes)

Question 9

Describe the clinical features of seborrheic dermatitis

Answer 9

Inflammatory reaction to the yeast Malassezia. Cradle cap in infants (large yellow scales), mild erythema, fine scaling, pruritis of face, eyebrow, eyelid, anterior chest, and external ear in young adults

Question 10

Define psoriasis

Answer 10

Chronic inflammatory dermatosis causing well-demarcated red scaly plaques

Question 11

Describe chronic plaque psoriasis

Answer 11

Salmon pink plaques with silver scale on the exterior aspects of knees, elbows, and scalp. Rubbing them causes pinpoint bleeding (Auspitz sign). Lesions also form at sites of trauma (Koebner phenomenon)

Question 12

Describe the histology of chronic plaque psoriasis

Answer 12

Parakeratosis, loss of granular layer, clubbing of rete ridges (test tubes in a rack appearance), Munro’s microabscesses

Question 13

Name at least 3 types of psoriasis

Answer 13

Chronic plaque psoriasis, flexural psoriasis, guttate psoriasis, erythrodermic/ pustular psoriasis

Question 14

Describe the nail changes associated with psoriasis

Answer 14

Psoriasis, onycholysis, subungal hyperkeratosis

Question 15

Describe flexural psoriasis

Answer 15

Seen later in life, usually affecting the groin, natal cleft, and sub-mammary arras

Question 16

Describe guttate psoriasis

Answer 16

Most common in children, rain drop plaque distribution, usually seen 2 weeks post-Strep throat

Question 17

Describe erythrodermic/ pustular psoriasis

Answer 17

Severe widespread psoriasis with systemic symptoms

Occasionally limited to hands and feet (palmo-plantar psoriasis)

Question 18

What % of those with psoriasis develop psoriatic arthritis?

Answer 18

5-10%

Question 19

Describe the lesions of lichen planus

Answer 19

5 Ps: Pruritic, Purple, Polygonal, Papules and Plaques with a mother-of pearl sheen and fine white network on their surface (Wickam’s striae), usually on inner surfaces of wrists but can affect oral mucous membrane (lacy appearance)

Question 20

Describe the histology of lichen planus

Answer 20

Hyperkeratosis with saw-toothing of rete ridges and basal cell degeneration

Question 21

Describe erythema multiforme

Answer 21

A combination of macules, papules, urticarial wheals, vesicles, bullae, and petechiae with annual target lesions, most commonly on the extensor surfaces of hands and feet

Question 22

Name 2 infectious causes of erythema multiforme

Answer 22

Herpes Simplex virus, Mycoplasma

Question 23

Name 5 drug causes of erythema multiforme

Answer 23

SNAPP: Sulphonamides, NSAIDs, Allopurinol, Penicillin, Phenytoin

Question 24

Describe pityriasis rosea

Answer 24

Salmon pink rash - herald patch - followed by oval macules in a Christmas tree distribution, appearing after a viral illness and remitting spontaneously

Question 25

Describe Stevens Johnson Syndrome

Answer 25

Sheets of skin detachment over <10% of the body’s surface area with prominent mucosal involvement. Nikolsky sign positive. Commonly caused by drugs (sulphonamides, anticonvulsants) and a dermatological emergency

Question 26

Describe toxic epidermal necrolysis

Answer 26

Sheets of skin detachment over >30% of the body’s surface area with prominent mucosal involvement. Nikolsky sign positive. Commonly caused by drugs (sulphonamides, anticonvulsants) and a dermatological emergency