Review Question - QID 217287

This unvaccinated patient who presents with postauricular lymphadenopathy, polyarticular arthralgia, low grade fever, and a descending maculopapular morbilliform rash most likely has rubella.

Rubella is an enveloped, icosahedral capsid, single-stranded, positive-sense RNA togavirus that commonly causes rash in unvaccinated patients. Patients will most commonly present with a low-grade fever associated with polyarthralgia and a descending maculopapular rash. Physical exam may occasionally reveal post-auricular lymphadenopathy. However, this symptom occurs prior to the rash/fever and may resolve prior to patient presentation. The classic rash in rubella is a fine, pink, non-confluent maculopapular rash that starts on the face and spreads to the trunk and extremities. Some patients may also have a petechial rash on the soft palate (known as Forschheimer spots) as well as orchitis. Diagnosis is confirmed with rubella-specific IgM antibody levels. Treatment consists of supportive care such as using antipyretic medications for fever.

Ogata et al. studied the duration between development of prodromal symptoms and the onset of a rash in patients with laboratory confirmed rubella. They found that the vast majority of patients had <2 days of delay before the onset of the characteristic rash seen in this disease. They recommended that other causes be considered when the time from onset of fever to onset of rash was 3 days or more since the likelihood of rubella was low.

Figure A is a clinical photograph showing a fine, pink, non-confluent maculopapular rash classically seen in patients with rubella.

Incorrect Answers:
Answer 1: Eczema, or atopic dermatitis, can also present with an erythematous rash in children. This rash is classically described as dry, pruritic skin located in the flexor surfaces of the arms and legs. It can occur in association with the atopic triad, consisting of eczema, allergic rhinitis, and asthma. Eczema would not cause a fever.

Answer 2: Measles can also present with a descending maculopapular rash. These patients often have a high grade fever and present with a prodrome of cough, coryza, conjunctivitis, and Koplik spots on the inside of the mouth. While these patients may present with a similar prodrome and rash, they are much sicker than those with rubella, making this less likely in this patient.

Answer 3: Parvovirus can also present with a rash in children. However, these patients are classically described as having a "slapped cheek" facial rash and would not have postauricular lymphadenopathy.

Answer 4: Roseola can also present with fever and a light pink morbilliform rash. The fever is usually high grade and the rash in this disease does not appear until after the fever resolves. This patient has a co-existent rash and fever.

Bullet Summary:
Rubella presents with postauricular lymphadenopathy, polyarticular arthralgia, low grade fever, and a descending maculopapular rash.