Acute/Chronic Infectious Dermatoses

Question 1

What is Impetigo?

Answer 1

A common superficial bacterial infection of the skin

Question 2

Who is most likely to get Impetigo?

Answer 2

Children and adults in poor health and hygiene, especially affecting hands and face

Question 3

What are the common bacteria causing Impetigo?

Answer 3

Beta-hemolytic streptococci and Staphylococcus aureus

Question 4

What histological feature is seen in Impetigo?

Answer 4

Spongiotic epidermis with heavy neutrophil infiltrate

Question 5

What are Verrucae (warts)?

Answer 5

Common lesions caused by human papillomaviruses (HPV)

Question 6

Who is most affected by Verrucae?

Answer 6

Children and adolescents, though they can affect any age

Question 7

What is the course of Verrucae?

Answer 7

Generally self-limited, regress spontaneously

Question 8

What is the most common type of Verruca?

Answer 8

Verruca vulgaris (hands mainly), elevated and dome-shaped

Question 9

What are the different types of Verrucae?

Answer 9

Verruca plana (flat wart), Verruca plantaris, Verruca palmaris, Condyloma acuminatum (venereal/genital wart)

Question 10

What is the appearance of Condyloma acuminatum?

Answer 10

Large, cauliflower-like genital warts

Question 11

What types of HPV cause anogenital warts?

Answer 11

HPV types 6 and 11

Question 12

What HPV types are associated with high risk?

Answer 12

HPV types 16 and 18, which can cause dysplasia and are linked with in situ squamous cell carcinoma of the genitalia, especially in the cervix

Question 13

Which other HPV types have been detected in skin lesions?

Answer 13

HPV types 5 and 8

Question 14

What histopathological features are seen in warts?

Answer 14

Hyperkeratosis, papillomatosis, hypergranulosis, vacuolated superficial keratinocytes with pyknotic, raisin-like nuclei (koilocytosis)

Question 15

What is Urticaria (Hives)?

Answer 15

LOCALIZED mast cell degranulation resulting in dermal microvascular hyperpermeability

Question 16

What are the clinical features of Urticaria?

Answer 16

Transient pruritic ‘Wheals’ lasting a few hours

Question 17

What triggers Urticaria?

Answer 17

Ag-induced release of mediators from mast cells due to food

Question 18

What type of hypersensitivity reaction is involved in Urticaria?

Answer 18

Type 1 hypersensitivity reaction (IgE-Ag interaction)

Question 19

What is the morphology of Urticaria?

Answer 19

Almost normal skin

Question 20

What is Acute Eczematous Dermatitis?

Answer 20

A clinical term for several conditions with different underlying causes

Question 21

What are the stages of Acute Eczematous Dermatitis?

Answer 21

Papulovesicular stage with oozing and crusted lesions
Later → Raised, scaly plaques

Question 22

What types of dermatitis are included in Acute Eczematous Dermatitis?

Answer 22

Allergic contact dermatitis

Question 23

What causes Allergic Contact Dermatitis?

Answer 23

CD4+ T cells and delayed hypersensitivity

Question 24

What is the genetic basis of Atopic Dermatitis?

Answer 24

Atopic dermatitis has a genetic basis

Question 25

What are the key features of the morphology of Acute Eczematous Dermatitis?

Answer 25

Spongiosis

Question 26

What other cells may be present in Acute Eczematous Dermatitis?

Answer 26

Eosinophils

Question 27

What is the appearance of lesions in Acute Eczematous Dermatitis?

Answer 27

Pruritic

Question 28

What is Erythema Multiforme?

Answer 28

Self-limited HS reaction to infections (HSV & mycoplasma) & drugs

Question 29

What cells are involved in Erythema Multiforme?

Answer 29

Cytotoxic CD8+ T cells

Question 30

What areas does Erythema Multiforme affect?

Answer 30

Skin and mucosal surfaces

Question 31

What are the characteristics of Erythema Multiforme lesions?

Answer 31

Variable erythematous lesions, sometimes with vesicles and targetoid lesions

Question 32

What are targetoid lesions?

Answer 32

Pale central blister (necrosis) surrounded by macular erythema and a halo in between

Question 33

What is the histology of Erythema Multiforme?

Answer 33

Perivascular inflammation, dermal edema, degeneration of keratinocytes ± epidermal necrosis in severe cases

Question 34

What is Stevens-Johnson Syndrome (SJS)?

Answer 34

Drugs-associated condition that may progress to more serious toxic epidermal necrolysis (TEN)

Question 35

What is the feature of SJS?

Answer 35

Keratinocyte necrosis and epidermal detachment, affecting <10% body surface area

Question 36

What is SJS/TEN overlap?

Answer 36

10-30% body surface area epidermal detachment, overlapping features of SJS and TEN

Question 37

What is Toxic Epidermal Necrolysis (TEN)?

Answer 37

Severe disease with full-thickness epidermal necrosis and detachment, >30% body surface area affected

Question 38

What are the risks of TEN?

Answer 38

Risk of infection, hypothermia, and dehydration

Question 39

What are the microscopic features in early lesions of TEN?

Answer 39

Apoptotic keratinocytes scattered in basal epidermis

Question 40

What are the microscopic features in later lesions of TEN?

Answer 40

Numerous necrotic keratinocytes, full-thickness epidermal necrosis, and subepidermal bullae

Question 41

What is Psoriasis?

Answer 41

A common scaly dermatosis associated with arthritis, myopathy, and enteropathy

Question 42

What type of immune response is Psoriasis mediated by?

Answer 42

Immunologically mediated by CD4+ TH17 and TH1 lymphocytes' homing to skin

Question 43

Which areas are most frequently affected in Psoriasis?

Answer 43

Elbows, knees, scalp, and glans penis (extensor surfaces)

Question 44

What is the most typical lesion in Psoriasis?

Answer 44

A well-demarcated pink plaque covered by loosely adherent scales with a salmon color

Question 45

What nail changes occur in Psoriasis?

Answer 45

Yellow to brown discoloration in 30% of cases

Question 46

What is the Koebner phenomenon in Psoriasis?

Answer 46

Psoriatic lesions can be induced by local trauma

Question 47

What are the microscopic features of Psoriasis?

Answer 47

Parakeratosis, mild hyperkeratosis, epidermal hyperplasia (regular acanthosis), loss of stratum granulosum

Question 48

What are Munro microabscesses in Psoriasis?

Answer 48

Neutrophils in parakeratotic scale

Question 49

What are the prominent features seen in the dermis in Psoriasis?

Answer 49

Prominent dermal capillaries and Auspitz sign (bleeding after removing the scales)

Question 50

What is Lichen Planus?

Answer 50

A cytotoxic CD8+ T cell response to a virus or drug

Question 51

What are the characteristic features of Lichen Planus?

Answer 51

3Ps: Pruritic Purple Papules that may coalesce to form plaques

Question 52

What are Wickham striae in Lichen Planus?

Answer 52

White lines seen on the papules

Question 53

Where do lesions of Lichen Planus typically appear?

Answer 53

Mainly on extremities, often around wrists and elbows

Question 54

What is the typical course of Lichen Planus?

Answer 54

Self-limited, resolves within 1-2 years leaving post-inflammatory hyperpigmentation

Question 55

How long may oral lesions of Lichen Planus persist?

Answer 55

Oral lesions may persist for years

Question 56

What is the microscopic finding in Lichen Planus?

Answer 56

Dense continuous (band-like) lymphocytic infiltrate at the dermoepidermal junction (lichenoid infiltrate)

Question 57

What changes occur in basal keratinocytes in Lichen Planus?

Answer 57

Vacuolar degeneration and necrosis

Question 58

What feature is seen at the dermoepidermal junction in Lichen Planus?

Answer 58

Zigzag pattern (Saw-tooth appearance)

Question 59

What are Civatte bodies in Lichen Planus?

Answer 59

Necrotic basal cells incorporated into the papillary dermis

Question 60

What other features are seen in Lichen Planus?

Answer 60

Acanthosis, hyperkeratosis, and hypergranulosis; parakeratosis should exclude LP as a differential diagnosis