Rubella
A 6-year-old unvaccinated girl develops a low-grade fever and aching in both wrists, followed the next day by a pink maculopapular rash that begins on the face and spreads to the trunk and limbs within 24 hours, fading by the third day. She has tender occipital, post-auricular and posterior cervical lymph nodes. There is no conjunctivitis, no coryza, no cough and no Koplik spots. Which is the most likely diagnosis?
- A.Measles
- B.Roseola infantum
- C.Erythema infectiosum
- D.RubellaCorrect
Explanation
Rubella, or German measles, is called the three-day rash disease because the fine pink maculopapular eruption starts on the face, spreads caudally within a day and clears by day three without staining or desquamation. Its most distinctive feature is tender lymphadenopathy in three characteristic sites, the suboccipital, post-auricular and posterior cervical nodes, which typically precedes the rash and persists for weeks. Constitutional symptoms are mild, and arthralgia or arthritis of the small joints is common in older girls and women. Measles is far more toxic, with a 3 to 4 day prodrome of high fever, cough, coryza and conjunctivitis, Koplik spots on the buccal mucosa, and a rash that spreads from the hairline downward, becomes confluent, lasts about a week and ends with brownish staining and desquamation. Roseola infantum affects infants and toddlers under 2 years, produces 3 to 5 days of high fever that resolves abruptly just as a rose-pink rash appears on the trunk, and may also show occipital adenopathy. Erythema infectiosum gives slapped-cheek erythema followed by a lacy reticular rash on the limbs that recurs with heat or sunlight. The greatest importance of rubella is its teratogenicity: infection in the first trimester causes congenital rubella syndrome with cataracts, sensorineural deafness and patent ductus arteriosus. Management is supportive, and prevention is achieved with two doses of the MMR vaccine, which must not be given during pregnancy.
Why each option
- A.
- Measles causes high fever with cough, coryza and conjunctivitis, Koplik spots, and a confluent rash lasting about a week that desquamates.
- B.
- Roseola occurs in children under 2 years, with high fever that abates abruptly as a truncal rash appears rather than fever and rash together.
- C.
- Erythema infectiosum produces slapped-cheek facial erythema followed by a lacy reticular rash on the extremities without prominent adenopathy.
- D.
- Correct. A pink maculopapular rash lasting three days with tender occipital, post-auricular and posterior cervical nodes is classic rubella.
Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024
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