Harvey's Garden

Measles

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Epidemiology

Etiology

  • Pathogen: Measles virus (Genus Morbillivirus, Family Paramyxoviridae).
  • Structure: Enveloped, negative-sense, single-stranded RNA virus.
  • Transmission: Respiratory droplets (highly contagious).
  • Virulence factors:
    • Hemagglutinin (H): Adhesion to host cells.
    • Fusion (F) protein: Viral entry; causes formation of multinucleated giant cells (syncytia).

Pathophysiology

Clinical features

Mnemonic

烧三天、疹三天、退三天

  • Prodrome (eg, cough, coryza, conjunctivitis, fever, Koplik spots)
  • Maculopapular exanthem
    • Cephalocaudal & centrifugal spread
    • Spares palms & soles

Complications

Common Complications (Respiratory and GI)

  • Pneumonia:
    • This is the most common cause of measles-related death in children.
    • Can be a secondary bacterial superinfection (e.g., S. pneumoniae, H. influenzae), which is most frequent.
    • Can also be a primary viral pneumonia, known as Hecht’s giant cell pneumonia. This interstitial pneumonitis is characterized by multinucleated giant cells and is often seen in immunocompromised patients but can occur in healthy individuals and carries a high fatality rate.
  • Otitis Media:
    • An extremely common secondary bacterial infection, occurring in up to 1 in 10 children with measles. Can lead to hearing loss.
  • Laryngotracheobronchitis (Croup):
    • Inflammation of the upper airways can lead to the characteristic “barking” cough and stridor.
  • Diarrhea:
    • Frequently reported and can lead to significant dehydration, especially in young children.

Subacute sclerosing panencephalitis (SSPE)

  • Etiology: Reactivation of defective Measles virus (mutated M protein); latency 7–10 years.
  • Hx: Young patient with history of measles (or unvaxed) presenting with school failure and personality changes.
  • Sx Progression: Behavioral regression → Myoclonus (jerking) → Dementia/Spasticity → Coma/Death.
  • CSF: ↑↑ Anti-measles antibodies, oligoclonal bands.
  • EEG: Periodic high-voltage slow waves.
  • Histo: Demyelination + Intranuclear viral inclusions in neurons/oligodendrocytes.
  • Tx: None (fatal).

Diagnostics

Childhood exanthems

FeatureRubella (German Measles)Measles (Rubeola)Scarlet FeverErythema Infectiosum (Fifth Dis.)Roseola Infantum (Sixth Dis.)Varicella (Chickenpox)
AgentTogavirus (RNA)Paramyxovirus (RNA)S. pyogenes (GAS) exotoxinParvovirus B19 (DNA)HHV-6, HHV-7 (DNA)VZV (HHV-3) (DNA)
ProdromeLow-grade fever, postauricular/occipital LAD, arthralgias.3 C’s: Cough, Coryza, Conjunctivitis. High fever.Fever, pharyngitis, headache, vomiting.Mild flu-like sx.High fever (>40°C) for 3-5 days, child appears well.Fever, malaise.
EnanthemForchheimer spots (petechiae on soft palate)Koplik spots (blue-white spots on buccal mucosa). Pathognomonic.Strawberry tongue, palatal petechiae.N/ANagayama spots (papules on soft palate).Ulcers in mouth/pharynx.
ExanthemMaculopapular rash starts on face, spreads caudally in <24h. Lighter than measles.Maculopapular rash starts at hairline, spreads caudally. Confluent.”Sandpaper” texture, diffuse erythema. Starts on trunk, spreads out. Spares palms/soles. Circumoral pallor.”Slapped cheeks” (malar rash), followed by lacy, reticular rash on trunk/extremities.Maculopapular rash appears as fever breaks. Starts on trunk, spreads to face/extremities.Vesicular rash on erythematous base (“dew drop on a rose petal”). Lesions in different stages. Starts on trunk, spreads to face/limbs.
Key Buzzwords”3-day measles”, postauricular LAD. Congenital: PDA, cataracts, deafness.Koplik spots, 3 C’s, SSPE (late complication).Sandpaper rash, strawberry tongue, Pastia’s lines (linear petechiae in flexures).Slapped cheeks, aplastic crisis (in SCD), hydrops fetalis.Fever first, then rash. Febrile seizures common.Pruritic vesicles in crops, Tzanck smear shows multinucleated giant cells. Reactivates as shingles.
TxSupportive. MMR vaccine for prevention.Supportive, Vit A. MMR vaccine for prevention.Penicillin or Amoxicillin (to prevent rheumatic fever).Supportive.Supportive.Supportive. Acyclovir in teens/adults/immunocompromised. Live-attenuated vaccine.

Fever-rash relationship

  • Measles (Rubeola): Fever first (with cough, coryza, conjunctivitis) → Rash appears 3-5 days later, spreading from head to toe.
  • Rubella (German Measles): Low-grade fever → Rash appears 1-2 days later, spreading quickly from head to toe.
  • Scarlet Fever: Fever and sore throat begin together → “Sandpaper” rash appears 1-2 days later.
  • Erythema Infectiosum (Fifth): Low-grade fever/prodrome resolves → “Slapped cheek” rash appears days later.
  • Roseola Infantum (Sixth): High fever for 3-5 days → Fever breaks → Rash appears after the fever is gone.
  • Varicella (Chickenpox): Fever and vesicular rash appear at the same time (lesions in various stages).
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Treatment

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