1. DERMATOLOGY

   1. Dermatitis

• Atopic dermatitis: what is Tx?

• MCQ: emollients and topical GCs for 10 d

• Child with itchy, erythematous, crusty eruption. DDx and 4 Tx?

• DDx: atopic dermatitis, nummular dermatitis, allergic contact dermatitis, scabies, psoriasis, tinea, drug eruption

• Tx (atopic dermatitis): avoid triggers, emollients, topical GCs, calcineurin inhibitors

• "Pruritic eruption" over child's finger web space, axilla, and neck web; sister has the same thing, but parents asymptomatic. What is the Dx (1 mark), 3 DDx (3 marks), the lab Ix that will definitively establish the Dx (1 mark), and most popular/standard Tx (1mark)?

• Dx: scabies Ix: microscopy (mites, ova feces)

• DDx: Urticaria Contact dermatitis Scabies Chicken pox Atopic dermatitis Bites

• Tx: permethrin 5% cream, 2 x 1wk apart for even asymptomatic family members

• A child presents to you with a diaper rash or is it? What else could it be?

• DDx: diaper candidiasis, irritant contact dermatitis, infantile psoriasis, others

2. 2. Rash/Exanthems

• A young ♂ with asthma gets a rash on his arms: itchy, red, and found on flexural surfaces. What are 2 possibilities?

• DDx: topic dermatitis, scabies, Pastia’s lines

• Rosy cheeks + lacy rash: give the Dx, causative organism, 1 complication, and Tx.

• Dx: erythema infectiosum (fifth disease) Causative agent: parvovirus B19

• Tx: NSAIDs (symptomatic arthropathy), otherwise none

• Complications: STAR (sore throat, arthritis, rash), glove and sock, aplastic crisis (sickle cell patients), fetal infection (anemia, fetal hydrops)

• Fever + erythematous rash: most likely Dx?

• MCQ: child is UTD on all immunizations, which eliminates 3 choices right away and narrows it down to either MRSA or GAS, take your pick ;-)

• Child with high fever x 4 days goes to walk-in clinic and gets amoxicillin. On the following day, he breaks out into generalized maculopapular rash.

• DDx (2 marks): Kawasaki disease, roseola, scarlet fever, drug reaction, etc.

• Tx (2 marks): depends on etiology

Definitions
MACULE
‐ Flat, circumscribed area of colour change
‐ Large (>1 cm) macule: patch
‐ E.g. vitiligo, port‐wine stain, café au lait
PAPULE
‐ Elevated, palpable lesion
‐ Large (>1cm) papule: plaque
‐ E.g. wart, mollusca
VESICLE
‐ Fluid‐filled elevation (pus, sanguinous)
‐ Large (>1 cm) vesicle: bulla
‐ E.g. impetigo
PUSTULE ‐ Circumscribed elevation of skin containing purulent exudate
‐ E.g. herpes simplex, varicella zoster
NODULE
‐ Palpable solid lesion
‐ Large (>1 cm) nodule: tumour
‐ E.g. dermatofibroma, nevi, benign or malignant tumours

• Primary lesion: caused at onset by disease process itself
• Secondary lesion: caused by progression of primary lesions or host
response to primary lesions (e.g., scratching) and develops over time
o E.g. scars, excoriations, fissures, crusts, ulcers, lichenification

Newborns
Common Bumps and Rashes
CONDITION - CLINICAL - MANAGEMENT
Acne neonatorum Closed comedones on forehead, nose, cheeks. Up to 20% Generally self‐resolves within 4 months without scarring

Erythema toxicum
neonatorum
Pustular eruption on face/trunk/proximal extremities
(spares palms, soles);‘flea‐bitten’ appearance
Self‐limiting – generally resolves over 5‐7 days, may last up to
several weeks

Infantile
hemangioma
Benign vascular tumour. Red appearance: 'strawberry
birthmark'
May grow rapidly but ultimately self‐resolving without treatment.
50% by age 5, 70% by age 7 and the remainder by age 12

Milia 1‐2 mm pearly, white or yellow papules. Occurs in up to
50%. Most often on forehead, cheeks, nose, chin
Self‐resolving within first month of life (up to 3 months)

Transient neonatal
pustular melanosis
Vesiculopustular rash; 5% of black newborns. Pustular
eruption without surrounding erythema; All areas of
body may be affected (including palms, soles)
Self‐limiting – collarette scale and pigmented macules fade over 3‐4
weeks

Diaper Rash
• Ask about: frequency of diaper changes, hx of skin disease, +/‐ diarrhea (irritant effect), improvement with therapy
• Consider infectious, irritant, inflammatory causes
ETIOLOGY CHARACTERISTICS TREATMENT
Diaper candidiasis
Beefy red plaques and confluent erosions.
Fine scale. Often painful
Satellite papules and pustules on
thigh/abdomen. Involves skin folds.
Topical antifungal: 1% clotrimazole, nystatin
Discontinue barrier creams

Irritant contact
dermatitis
Shiny erythematous rash. Macerations and
erosions if severe.
Unaffected skin folds
Barrier creams: zinc oxide +/‐ low potency steroid cream (1% hydrocortisone)
Diapers: more frequent changes, use disposable (chronic irritation)
May co‐exist with candidiasis

Infantile psoriasis Sharply demarcated erythematous
papules/plaques involving skin folds
None

Other (if rash persistent): zinc deficiency, rarely immunologic/metabolic disease (HIV, Langerhan's cell histiocytosis)

Childhood
Common Rashes
CONDITION ETIOLOGY CHARACTERISTICS MANAGEMENT
Scabies Scabies mite Polymorphic macules, pustules, excoriations,
nodules. Pruritic eruption without xerosis
Usually spares face
Ask about itchy family members
Contagious precautions
Permethrin (Nix) 5% cream for patient and family
members (even if asymptomatic); 2 applications,
1 week apart

Impetigo
S. aureus infection "Honey‐coloured crusted ooze on face, extremities"
Other etiology: Group A β‐hemolytic streptococcus
Oral antibiotic (i.e. cephalexin/ erythromycin)
IV therapy if severe

Tinea Dermatophyte (fungal)
infection
Head – tinea capitis
Body – tinea corporis
Nail – onychomycosis
Topical anti‐fungals for skin
Systemic anti‐fungals for nails/head (i.e.
terbinafine)

Urticaria Various triggers for
histamine release
Evanescent, migratory eruption; itchy. <48h duration Stop offending agent
Anti‐histamines

Molluscum
contagiosum
Viral infection (pox
virus)
"Dome‐shaped pearly flesh‐coloured to translucent
umbilicated lesions". Common on trunk, face,
extremities. Often pruritic. No systemic
manifestations
Mostly self‐resolving (less likely to clear if atopic).
Treatment options: cantharidin (keratolytic),
curretage, watch‐and‐wait, cryotherapy (may
cause pain/scarring)

Exanthems
• Skin eruptions + fever
• Often associated with enanthems (mucosal involvement of exanthems) 􀃆 look in the mouth!
Differential Diagnosis
DISEASE ID CLINICAL MANAGEMENT COMPLICATIONS
Measles Incubation 8‐13d;
Infectious 4d before and
after rash;
Respiratory isolation
Morbiliform rash – starts at hairline and
spreads to face/neck/trunk;
Conjunctivitis + cough + coryza‐(3 C’s)
Enanthem: Koplik spots on buccal
mucosa
Patient: vitamin A
Contacts: Ig & MMR
vaccine
Prevention: MMR vaccine
Pneumonia, otitis media,
encephalitis, myocarditis (rarely)

Rubella Incubation 14‐21d;
Infectious 7d before and
after rash
Pink, maculopapular rash on
face/neck/trunk;
Occipital and retroauricular nodes;
Low‐grade fever
Symptomatic treatment
Prevention: MMR with
booster
STAR complex (sore throat, arthritis,
rash)
Congential anomalies if contracted in
pregnancy

Roseola Incubation 5‐15d;
HHV‐6
Pink, maculopapular rash on
neck/arms/trunk
Symptomatic treatment Febrile seizures

Erythema
infectiosum
(aka: Fifth
Disease)
Incubation 4‐14d;
Parvovirus B19
Red, flushed (‘slapped’) cheeks;
Maculopapular ‘lacy’ rash;
May reappear months later with
exercise/sun exposure
Symptomatic treatment STAR complex
‘Glove & sock’ distribution
Aplastic crisis (particularly sickle cell
patients)

Chicken
pox (VZV)
Incubation 10‐21d;
Infectious 1‐2d pre‐rash
to 5d post‐rash;
Respiratory isolation
Itchy, vesiculo‐bullous rash +/‐
macules/papules/crusts with crops of
skin lesions every 2‐3d
"Dew drops on a rose petal"
Symptomatic treatment
Prevention: VZIG within
96h from contact;
varicella vaccine
Skin: bacterial super‐infection,
necrotizing fasciitis
CNS: encephalitis, cerebellar ataxia
Systemic: hepatitis, DIC

Herpes
simplex
HHV‐1, ‐2 Grouped vesicles with erythematous
base +/‐ exanthems
Topical or oral antivirals Local: skin infection, keratitis,
gingivostomatitis
CNS: encephalitis
Systemic: hepatitis, DIC

Handfootmouth
disease
Coxsackie group A Vesicles and pustules with
erythematous base; Enanthems
(tongue, posterior pharynx)
Symptomatic treatment Dehydration

GianottiCrosti
syndrome
Associated with EBV,
HBV, coxsackie,
parvovirus
Asymptomatic papular acrodermatitis;
Preceded by viral prodrome
Self‐limiting: resolves in
3‐12 weeks)

Scarlet
fever
Group A strep Generalized, red papules with ‘sandpaper’
texture;
Flexural accentuation (‘Pastia’s lines’);
Desquamation;
Enanthems (strawberry tongue,
petechiae on palate)
Penicillin V/ampicillin /
amoxicillin x10 days
(macrolide if pen
allergic)
Pneumonia, pericarditis, meningitis,
hepatitis, glomerulonephritis,
rheumatic fever

Kawasaki
disease
Unknown etiology Fever ≥5 days + 4 of 5:
‐ unilateral lymphadenopathy
‐ red, cracked lips / strawberry tongue
‐ edema, erythema of palms & soles
‐ generalized, maculopapular rash
‐ non‐purulent bilateral conjunctivitis
High‐dose ASA, IVIG,
Baseline echo & repeat in
6 weeks
Coronary artery aneurysm

Common Enanthems
• Erythema infectiosum – non‐blanchable petechiae in mouth
• Enteroviral exanthems – vesicles / erosions in posterior mouth
• Herpes infection – ulcers / erosions in anterior mouth
• Kawasaki disease – red, cracked lips; strawberry tongue; red mouth and buccal mucosa

Dermatitis
Differential Diagnosis of Dermatitis
• describes red, inflammatory skin changes with poorly demarcated borders and common histology
DISEASE MORPHOLOGY ASSOCIATED FEATURES DISTRIBUTION PRURITIS
Atopic
dermatitis
Papules / plaques of edema,
erythema; excoriation, lichenification
Generalized dryness (xerosis) Infants – face, extensor surfaces
Children – flexural areas
Adults – face, dorsum of feet & hands,
eyelid
++

Seborrheic
dermatitis
Yellow, greasy scaly, red plaques Maceration Folds, scalp, diaper area Absent

Nummular
dermatitis
Coin‐shaped plaques; edema,
erythema, crusting
Normal skin Anywhere, particularly on lower legs +++

Scabies Burrows in web spaces;
polymorphous eruption of papules,
vesiculopustules, nodules
Normal skin Finger and toe webs, folds, genitalia
Infants: pustules on palms, soles
+++

Allergic contact
dermatitis
Red papules, plaques, vesicles, bullae Localized to contact area (ie.
belt buckle, shirt buttons)
Erosions, crusting, super (2o bacterial)
infection
++

Eczema
• Mostly used interchangeably with atopic dermatitis
Management
• Skin care: emollients and moisturizers to improve xerosis; avoid triggers
• Topical corticosteroids for flare control ex. mid‐to‐high potency corticosteroid application bid for 7‐10d then re‐evaluate
• Once a flare is controlled, shift to lower potency cream used intermittently for maintenance
• Topical calcineurin inhibitors may also be used for flare control and maintenance. Useful in persistent disease, frequent flares and areas of
skin sensitive to systemic absorption and atrophy
Eczema herpeticum
• Severe and even lethal complication of atopic dermatitis‐‐ may lead to blindness or mortality
• Disseminated skin infection due to herpes simplex (HSV): fever + grouped 'punched‐out' erosions
• Treat urgently with high dose systemic antiviral therapy (oral/IV acyclovir), Ophthalmology assessment if near eyes

Papulosquamous Eruptions
• red, scaly, itchy lesions with common morphology
• hyperkeratotic and well‐demarcated in contrast to dermatitis (classically psoriasis)
Differential Diagnosis of Papulosquamous Eruptions
DISEASE MORPHOLOGY ASSOCIATED FEATURES DISTRIBUTION PROPOSED ETIOLOGIES
Psoriasis Papulosquamous plaques with
silvery scale
Auspitz sign – bleeding with
removal of scales;
Nail pitting, onycholysis;
Arthritis;
+ pruritus
Extensor surfaces, scalp, genitalia,
gluteal folds
Group A streptococcus
Genetic

Pityriasis
rosea
Large, ‘herald patch’; smaller
erythematous papules with
central scales
+/‐ pruritus ‘Christmas tree’ distribution on
trunk
HHV‐7

Tinea
corporis
Round, red plaques with
central clearing and raised
active border
‐‐‐ Trunk, extremities, face Dermatophyte (microsporon,
epidermophyton,
trichophyton)

Drug
eruption
Isolated or multiple
erythematous papules and
plaques with fine scales
+/‐ fever, eosinophilia Anywhere Erythromycin,
metronidazole, sulfonamides