Skin Pathology Flashcards
Define hyperkeratosis
Thickening of the stratum corneum, leading to increased keratin
Define acanthosis
Thickening of stratum spinosum
Define spongiosis
Intercellular oedema
Define lentiginous
Linear pattern of melanocyte proliferation within the epidermal basal cell layer. Can be reactive or neoplastic
Describe the histological appearance of acute dermatitis
Spongiosis, inflammatory infiltrate in dermis, dilated dermal capillaries
Describe the histological appearance of chronic dermatitis
Acanthosis, crusting, scaling
Describe the clinical features of atopic dermatitis
Inflamed, dry itchy rash on face and scalp of infants or flexural surfaces of children
Describe the clinical features of contact dermatitis
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)
Describe the clinical features of seborrheic dermatitis
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
Define psoriasis
Chronic inflammatory dermatosis causing well-demarcated red scaly plaques
Describe chronic plaque psoriasis
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)
Describe the histology of chronic plaque psoriasis
Parakeratosis, loss of granular layer, clubbing of rete ridges (test tubes in a rack appearance), Munro’s microabscesses
Name at least 3 types of psoriasis
Chronic plaque psoriasis, flexural psoriasis, guttate psoriasis, erythrodermic/ pustular psoriasis
Describe the nail changes associated with psoriasis
Psoriasis, onycholysis, subungal hyperkeratosis
Describe flexural psoriasis
Seen later in life, usually affecting the groin, natal cleft, and sub-mammary arras
Describe guttate psoriasis
Most common in children, rain drop plaque distribution, usually seen 2 weeks post-Strep throat
Describe erythrodermic/ pustular psoriasis
Severe widespread psoriasis with systemic symptoms
Occasionally limited to hands and feet (palmo-plantar psoriasis)
What % of those with psoriasis develop psoriatic arthritis?
5-10%
Describe the lesions of lichen planus
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)
Describe the histology of lichen planus
Hyperkeratosis with saw-toothing of rete ridges and basal cell degeneration
Describe erythema multiforme
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
Name 2 infectious causes of erythema multiforme
Herpes Simplex virus, Mycoplasma
Name 5 drug causes of erythema multiforme
SNAPP: Sulphonamides, NSAIDs, Allopurinol, Penicillin, Phenytoin
Describe pityriasis rosea
Salmon pink rash - herald patch - followed by oval macules in a Christmas tree distribution, appearing after a viral illness and remitting spontaneously
Describe Stevens Johnson Syndrome
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
Describe toxic epidermal necrolysis
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
