What to do if a child develops erythema?

Evaluation of Erythema in a 7-Year-Old Child

When a 7-year-old child develops erythema (redness), the immediate priority is to determine whether this represents a benign condition like atopic dermatitis or a life-threatening emergency such as eczema herpeticum, Stevens-Johnson syndrome, or acute rheumatic fever.

Immediate Assessment Priorities

Critical Red Flags Requiring Urgent Evaluation

You must immediately rule out the following life-threatening conditions:

• Eczema herpeticum: Look for multiple uniform "punched-out" erosions or vesiculopustular eruptions, which constitute a dermatologic emergency requiring immediate systemic acyclovir 1, 2, 3
• Stevens-Johnson syndrome/Toxic Epidermal Necrolysis: Assess for widespread erythematous or purpuric macules with blisters, mucosal involvement (mouth, eyes, genitalia), and epidermal detachment 4, 5, 6
• Acute rheumatic fever: Examine for erythema marginatum (evanescent pink rash with pale centers and rounded margins on trunk and proximal extremities, not facial) along with fever, arthritis, or carditis 4
• Meningococcemia: Check for petechiae/purpura, hemodynamic instability, and fever 7

Essential History Elements

Obtain the following specific information:

• Onset and progression: Age of onset (before 6 months suggests congenital atopic dermatitis or mastocytosis), duration of individual lesions (fixed >7 days suggests erythema multiforme vs. <1 day for urticaria) 1, 5
• Distribution pattern: Flexural areas (elbows, neck) suggest atopic eczema; trunk and extremities suggest mastocytosis; acral and extensor surfaces suggest erythema multiforme 1, 5, 6
• Associated symptoms: Pruritus (mandatory for atopic dermatitis), pain, fever, systemic symptoms (flushing, diarrhea for mastocytosis) 4, 1
• Triggers: Recent infections (HSV, Mycoplasma pneumoniae), medications, vaccinations, temperature changes 8, 5, 6
• Family history: Atopy (asthma, hay fever, eczema) strongly supports atopic dermatitis 4

Physical Examination Specifics

Systematically assess the following:

• Skin lesion morphology: Target lesions (erythema multiforme), vesicles/erosions (eczema herpeticum), serpiginous margins (erythema marginatum), urtication on rubbing/Darier sign (mastocytosis) 4, 1, 5
• Distribution: Document percentage of body surface area involved, whether skin folds are affected, presence of satellite lesions 4, 3
• Signs of infection: Honey-colored crusting, weeping, or extensive crusting suggests secondary bacterial infection requiring antibiotics 4, 2, 3
• Mucosal involvement: Examine mouth, eyes, and genitalia for erosions or inflammation 4, 5
• Vital signs: Fever >38°C, tachycardia, respiratory rate, capillary refill time 4, 9

Diagnostic Algorithm

Step 1: Rule Out Emergencies

If ANY of the following are present, initiate emergency management immediately:

• Vesicular/erosive lesions with uniform "punched-out" appearance: Start systemic acyclovir immediately for presumed eczema herpeticum (do not wait for confirmatory testing) 1, 2, 3
• Widespread blistering with mucosal involvement: Hospitalize for Stevens-Johnson syndrome/TEN; obtain dermatology and ophthalmology consultations within 24 hours 4
• Petechiae/purpura with fever and hemodynamic instability: Treat as meningococcemia with immediate antibiotics 7

Step 2: Identify Common Benign Conditions

If no red flags are present, consider these diagnoses:

Atopic Dermatitis (Most Common)

Diagnose clinically if the child has pruritus PLUS three or more of the following:

• History of involvement of flexural areas (or cheeks/forehead in children <4 years) 4, 1
• Personal or family history of atopy 4
• Generalized dry skin in the past year 4
• Visible flexural eczema 4

Management approach:

• Apply emollients liberally and frequently (at least twice daily) 4, 2
• Use low-potency topical corticosteroids (hydrocortisone) for face/flexures, moderate-potency for trunk/limbs 4
• Avoid soaps and irritants; use soap substitutes 4

Erythema Multiforme

Suspect if:

• Typical or atypical target lesions present symmetrically on extremities (especially extensor surfaces) 5, 6
• Individual lesions fixed for minimum of 7 days 5
• Recent HSV infection or Mycoplasma pneumoniae (obtain serology) 8, 5, 6

Management approach:

• Symptomatic treatment with topical corticosteroids or antihistamines 8, 5
• If HSV-associated and recurrent, initiate prophylactic antiviral therapy 5, 6
• If Mycoplasma suspected, treat with azithromycin 6

Mastocytosis

Suspect if:

• Onset before 6 months of age 1
• Positive Darier sign (urtication on rubbing) present in 89-94% of cases 1
• Reddish-brown macules or papules on trunk and extremities 1

Workup includes:

• Serum tryptase level, complete blood count, skin biopsy with tryptase immunostaining 1

Step 3: Assess for Secondary Infection

Add empirical antibiotics if ANY of the following are present:

• Honey-colored crusting, weeping, or extensive crusting 4, 2, 3
• Deterioration of previously stable eczema 4
• Antibiotic choice: Flucloxacillin (or cephalexin in penicillin allergy) to cover Staphylococcus aureus 2, 3
• Obtain bacterial swabs for culture and sensitivity 4

Common Pitfalls to Avoid

Never miss eczema herpeticum: Any deterioration of eczema with grouped vesicular lesions requires urgent viral culture/PCR and immediate systemic acyclovir without waiting for results 4, 1, 3

Do not confuse erythema multiforme with Stevens-Johnson syndrome: Erythema multiforme has typical target lesions on acrally distributed sites, while SJS has widespread purpuric macules with blisters and significant mucosal involvement 5, 6

Do not rely solely on fever height: In acute rheumatic fever, fever may be >38°C in high-risk populations but can be lower; focus on the constellation of findings 4

Reassess if no improvement within 1-2 weeks: If initial management fails, reconsider the diagnosis and obtain dermatology referral 3