Parvovirus B19 - Microbiology - Medbullets Step 1

Snapshot

A 25-year-old woman presents to the emergency room for painful joints. She has had pain in her bilateral hands and wrists for the past few days. She also had a low-grade fever and mild upper respiratory symptoms. She is 14-weeks pregnant and has had good prenatal care. She works as a kindergarten teacher. On physical exam, the joint in her hands are slightly swollen and tender. A fetal ultrasound shows hydrops fetalis.

Introduction

Classification
- parvovirus B19
  - non-enveloped, linear, single-stranded DNA virus
  - causes a variety of diseases
    - aplastic crisis in patients with red blood cell disorders
    - pure red blood cell aplasia in adults
    - rheumatoid arthritis-like symptom in adults
    - erythema infectiosum (fifth disease) in children
    - hydrops fetalis in fetuses if pregnant women are infected
  - transmission via respiratory droplets
Epidemiology
- incidence
  - highest in winter and spring
- demographics
  - children > adults
- risk factors
  - sickle cell disease
  - thalassemia
  - hereditary spherocytosis
  - close proximity to others (e.g., school or daycare centers)
Pathogenesis
- infects red blood cells through the P antigen
- viral replication in bone marrow causes the death of erythroid progenitor cells
- causes hydrops fetalis in fetuses due to severe fetal anemia

Presentation

Symptoms
- prodrome with flu-like symptom
- hydrops fetalis and fetal death in pregnant women
- polyarthropathy
  - small joints (e.g., hands)
Physical exam
- erythema infectiosum
  - first rash appears as slapped cheeks
  - subsequent rash is an erythematous maculopapular rash on the trunk and limbs, which may appear reticular or lacy

Studies

Labs
- parvovirus-specific immunoglobulin M
- detection of parvovirus on polymerase chain reaction
- anemia
- low or absent reticulocyte
Making the diagnosis
- based on clinical presentation
- may be confirmed with laboratory studies

Differential

Measles
- distinguishing factors
  - confluent maculopapular rash without slapped cheeks rash
  - Koplik spots on buccal mucosa
Rubella
- distinguishing factor
  - non-confluent maculopapular rash that spreads from face to body

Treatment

Management approach
- mainstay of treatment is supportive care
Conservative
- supportive care
  - indication
    - all patients
  - modalities
    - analgesics
    - hydration
Medical
- non-steroidal anti-inflammatory drugs
  - indication
    - polyarthropathy

Complications