A 5 year old girl with fever and rash

Question

What is the most likely diagnosis?

Answer

Measles (rubeola), with associated rash, conjunctivitis, and Koplik’s spots (bluish-white enanthem with a surrounding red halo on the buccal mucosa),23 in a child who has received partial immunisation.

The typical incubation period of measles is seven to 18 days. The infection is contagious for four days before and four days after the appearance of a diffuse, blotchy, maculopapular, itchy or non-itchy erythematous skin rash.2345

Conjunctivitis, coryza, and cough (the three Cs), as well as fever and maculopapular rash are the key symptoms of measles.567

Koplik’s spots are present in at least 70% of patients and appear in the prodromal phase68; these persist for three to four days and disappear during the rash phase.

Several conditions present with oral lesions similar to Koplik’s spots, including Fordyce aphthae (no red halo), aphthous ulcers (painful, ulcerative, usually larger, and less numerous), and parvovirus B19 infection (slapped cheek rash).8

Complete measles immunisation (two doses) is necessary for adequate maintenance of immunity, prevention of transmission and outbreaks, and herd immunity.679101112 The pooled immunity rate for the measles vaccine is about 93% for one dose (39-100%, age ≥11 years) and 97% for two doses (67-100%, age ≥15 years).11

Modified measles refers to measles in people with partial immunity, including patients given immunoglobulin as postexposure prophylaxis, infants with some residual maternal antibody, and patients who have received only one vaccination dose. Patients with modified measles might have a prolonged incubation period, less severe prodrome, and milder or subclinical symptoms, with discrete rashes of shorter duration.121314

Consider measles in patients with a history of travel from endemic areas, despite previous vaccination history, particularly if Koplik’s spots are suspected.

Covid-19 considerations

Reduced international travel, lockdown, and physical distancing during the coronavirus disease 2019 (covid-19) pandemic might reduce the spread of measles. Restrictions, however, might also affect measles vaccination programmes,15 and patients with modified measles may be presumed to have covid-19, thereby preventing appropriate measles contact tracing and postexposure prophylaxis.

Learning points

• In patients with fever, look for features of measles such as Koplik’s spots, especially in those with a travel history, contact history, or incomplete immunisation.

• Encourage complete measles vaccination and ensure appropriate public health measures when measles is suspected.

Patient outcome

A clinical diagnosis of measles was made and the patient was isolated immediately and treated with supportive care. Measles is a notifiable disease in Taiwan. Three days later, the Taiwan Centers for Disease Control confirmed the diagnosis of measles from increased serum levels of measles immunoglobulin M and positive polymerase chain reaction results for both nasal swab and urine. The patient recovered uneventfully.