What is the diagnosis and treatment for a patient presenting with erythema of the hands and feet without local rashes, and a vesicular rash on the abdomen?

Kawasaki Disease is the Most Likely Diagnosis

Based on the clinical presentation of erythema of hands and feet without local rashes, combined with a vesicular rash on the abdomen, Kawasaki disease should be strongly considered and requires urgent evaluation and treatment to prevent coronary artery complications.

Critical Diagnostic Reasoning

The key to this diagnosis lies in recognizing that vesicular and bullous lesions are NOT consistent with Kawasaki disease 1. However, the erythema of hands and feet is a cardinal feature of Kawasaki disease, and the "vesicular" appearance on the abdomen may actually represent:

• Misidentified maculopapular or erythema multiforme-like rash that can occur in Kawasaki disease, which is commonly truncal with groin accentuation 1
• The rash in Kawasaki disease can appear urticarial, scarlatiniform, or erythema multiforme-like, but true vesicles should prompt reconsideration 1

Immediate Assessment Required

Evaluate for the five principal clinical features of Kawasaki disease 1:

1. Fever ≥5 days (or ≥4 days with 4 principal features) - temperature >39°C (102.2°F) 1
2. Extremity changes - erythema and edema of hands/feet in acute phase (present in this case), with periungual desquamation appearing 2-3 weeks later 1
3. Polymorphous rash - typically maculopapular, truncal, with groin accentuation 1
4. Bilateral conjunctival injection - nonexudative, bulbar, sparing the limbus 1
5. Oral mucosal changes - red cracked lips, strawberry tongue, diffuse oral erythema 1
6. Cervical lymphadenopathy - ≥1.5 cm diameter, usually unilateral (least common feature) 1

Diagnosis requires fever plus ≥4 of the 5 principal features 1.

Alternative Diagnoses to Exclude

If true vesicles are confirmed on examination, consider:

Hand, Foot, and Mouth Disease (HFMD)

• Vesicular lesions on hands, feet, AND oral mucosa are characteristic 2
• Can present with widespread vesicular exanthema involving trunk, buttocks, arms, and legs 2
• Peri-oral rash particularly associated with coxsackievirus A6 2
• Key difference: HFMD has vesicles ON the hands and feet, not just erythema 2

Disseminated Lyme Disease

• Secondary erythema migrans lesions can occur on abdomen via hematogenous spread 1
• Vesicles or pustules present at the center of primary erythema migrans in ~5% of cases 1
• Key difference: Lyme lesions are expanding erythematous patches ≥5 cm, not true vesicular rash 1
• Requires tick exposure history and appropriate geographic location 1

Eczema Herpeticum

• Rapidly progressive vesicular eruption in patients with underlying atopic dermatitis 3
• Presents with many uniformly shaped and sized eroded vesicles 3
• Key difference: Requires pre-existing skin disorder and vesicles are widespread, not isolated to abdomen 3

Urgent Treatment Protocol

If Kawasaki disease is confirmed or strongly suspected 1, 4:

First-Line Treatment (Evidence Level A)

• IVIG 2 g/kg as single infusion over 10-12 hours 1, 4
• High-dose aspirin 80-100 mg/kg/day divided into 4 doses, given with IVIG 1, 4
• Continue high-dose aspirin until afebrile for 48-72 hours 4
• Then reduce to low-dose aspirin 3-5 mg/kg/day once daily for 6-8 weeks 4

Critical Timing

• Treatment must be initiated within 10 days of fever onset to prevent coronary artery aneurysms 1, 4
• Fever typically resolves within 36 hours after IVIG completion 1
• If fever persists beyond 36 hours post-IVIG, patient has IVIG resistance requiring additional therapy 1

Essential Diagnostic Workup

Before treatment, obtain 1, 4:

• Complete blood count (expect leukocytosis, later thrombocytosis) 1
• C-reactive protein and erythrocyte sedimentation rate (elevated) 1
• Serum albumin (low) and transaminases (elevated) 1
• Urinalysis (sterile pyuria) 1
• Echocardiography - mandatory even in first 10 days to detect early coronary abnormalities 1

Critical Pitfalls to Avoid

• Do not exclude Kawasaki disease based on presence of "vesicles" - carefully re-examine the rash morphology, as maculopapular and erythema multiforme-like rashes can be misidentified 1
• Do not wait for all 5 principal features to appear simultaneously - they typically evolve over time 1
• Do not delay treatment beyond day 10 of fever - risk of coronary complications increases significantly 1, 4
• True vesicular or bullous lesions should prompt search for alternative diagnosis 1
• Exudative conjunctivitis, exudative pharyngitis, or oral ulcerations argue against Kawasaki disease 1