203.4 📌 章末速蚘

  • Parvovirus B19: smallest DNA virus, P antigen receptor on erythroid progenitors
  • 5 forms:
    1. Erythema infectiosum (5th disease) — children, “slapped cheek”
    2. Arthropathy — adults (women), symmetric small joint
    3. Aplastic crisis — chronic hemolytic anemia (sickle cell, HS, thalassemia); transfusion
    4. Hydrops fetalis — pregnancy; MCA Doppler-guided intrauterine transfusion
    5. Chronic anemia / pure red cell aplasia — immunocompromise (HIV, transplant); IVIG
  • Dx: serology (IgM acute, IgG past), PCR
  • “Lantern cells” (giant pronormoblasts) on marrow biopsy pathognomonic
  • Contagious before rash, not after
  • MCA Doppler PSV > 1.5 MoM = fetal anemia threshold
  • Pregnancy management: serial US + MCA Doppler + intrauterine transfusion if needed
  • HCW exposure pregnancy: serology + case-by-case
  • 1st measles, 2nd scarlet, 3rd rubella, 5th parvovirus, 6th HHV-6 — classic rash numbering