Diagnosis

Erythema infectiosum

Etiology

Cause [esi]

• Human parvovirus B19

Pathophysiology [esi]

1. Mode of transmission: droplets from respiratory secretions or hematogenous spread

2. Acute infection --> Th1–mediated cellular immune response

3. Production of specific IgM antibodies and subsequent formation of immune complexes

4. Deposition of the immune complexes in the skin and joints --> signs and symptoms

   • Phase 1: First 2-4 days starts with an exanthem on the cheeks (slapped-cheek)

   • Phase 2: Next 1-4 days --> erythematous maculopapular rash on proximal limbs

   • Phase 3: Frequent clearing and recurrences for weeks or months

Complications [esi]

• Arthritis

• Aplastic anemia

• Fetal infection --> miscarriage, intrauterine fetal demise, and hydrops fetalis

Epidemiology

Incidence per 100.000 [o2g]

Approach

• ELISA (serologic testing for immunoglobulin M and immunoglobulin G antibodies) [esi]

• PCR

Treatment

1. No specific antiviral therapy is available

2. A benign and self-limited disease: Symptomatic treatment

   • Fever, arthralgia, headache --> Acetaminophen or NSAIDs

   • Pruritus --> antihistamines or topical antipruritic lotions

   • Sun protection or avoidance

   • Aplastic crisis --> blood transfusion

   • Pregnant patient --> follow-up with an obstetrician

Differential diagnoses

Acute rheumatic fever, Anaphylaxis, Drug eruptions, Erythema infectiosum, Hand-Foot-and-Mouth disease, Influenza, Lyme disease, Measles, Mononucleosis, Mumps, Reactive arthritis, Rheumatoid arthritis, Roseola infantum, Rubella, Scarlet fever, Systemic lupus erythematosus, Viral hepatitis