203.3 🩺 內科專科考前版

203.3.0.1 1⃣ Pregnancy Management Algorithm

  1. Maternal exposure to known case / school outbreak
  2. B19 IgM + IgG serology at presentation
  3. If IgG +, IgM - = immune, no further action
  4. If IgM + or IgG - = at risk, consult MFM
  5. Serial fetal ultrasound + MCA Doppler q1-2 wk × 8-12 wk
  6. MCA Doppler PSV > 1.5 MoM = fetal anemia
  7. Cordocentesis + intrauterine transfusion
  8. After transfusion: continued monitoring; usually 1-2 transfusions sufficient

203.3.0.2 2⃣ Sickle Cell Aplastic Crisis Workup

  • Acute drop in Hb
  • Low reticulocyte (vs normal high in hemolytic anemia)
  • B19 IgM + or PCR +
  • Other causes: G6PD deficiency hemolysis, splenic sequestration (rare adult)
  • Transfusion + supportive

203.3.0.3 3⃣ Healthcare Worker Exposure During Pregnancy

  • Pregnant HCW + 5th disease exposure → counseling
  • Serology to determine immunity status
  • If non-immune → ideally avoid further exposure
  • Most cases asymptomatic; severe hydrops rare
  • 䞍 mandatory to reassign work in all cases — case-by-case

203.3.0.4 4⃣ B19 in Solid Organ Transplant

  • 1-2% kidney transplant
  • Pre-transplant donor / recipient serology not routine
  • Post-transplant chronic anemia + persistent B19 viremia → IVIG
  • Reduce immunosuppression
  • Repeat IVIG if recurrent

203.3.0.5 5⃣ B19 + HIV

  • Advanced HIV (CD4 < 100) → chronic infection + persistent anemia
  • IVIG 2 g/kg divided over 5 days
  • ART → immune reconstitution → clears virus over months
  • Surveillance for relapse

203.3.0.6 6⃣ B19 + Vasculitis Mimics

  • Some reports of B19-associated vasculitis (PAN-like, ANCA-related)
  • Rare
  • Serology + PCR + biopsy in some workups

203.3.0.7 7⃣ Erythroviridae Family

  • B19 = species
  • Erythroparvovirus genus
  • Parvoviridae family
  • AAV (adeno-associated virus) — gene therapy vector (non-pathogenic)
  • Bocavirus — respiratory + GI in children (newer, separate genus)

203.3.0.8 8⃣ 健保 / Taiwan

  • 健保 B19 serology (limited indication)
  • 健保 IVIG for confirmed indication
  • Pregnancy MCA Doppler — perinatology
  • Sickle cell rare Taiwan (vs Africa)
  • Hereditary spherocytosis, thalassemia common — awareness in aplastic crisis

203.3.0.9 9⃣ Adult Polyarthritis Differential

Disease Features
Parvovirus B19 Symmetric small joint, self-limited 2-4 wk
RA Symmetric small joint, persistent, RF + Anti-CCP +
Lupus Other organ involvement, ANA +
Reactive arthritis Asymmetric, post-GI/STD
Viral (HCV, HBV) Test viral serology
Crystal Mono / oligoarticular, fluid crystals

203.3.0.10 10. Vaccine

  • No FDA-approved B19 vaccine yet
  • Candidates in development
  • Universal seroprevalence reduces vaccine impact