What is the clinical significance of a lacy, macular rash following a rapidly resolved fever?

A lacy, macular rash on the trunk that follows the resolution of a fever is pathognomonic for Roseola infantum (caused by HSV-6), which is most commonly seen in infants aged 9-12 months.

The childhood exanthems can be differentiated based on their prodrome and progression. Erythema infectiosum (5th disease, caused by Parvovirus), which usually occurs in children 5-7 yoa, typically present with a mild fever and blotchy pink “slapped cheek” rash that spreads to the trunk and extremities. Measles (Rubeola, caused by Paramyxovirus) classically causes a maculopapular rash that spreads from the head downwards, with high fever, photophobia, cough, coryza, conjunctivitis and Koplik’s spots. The presentation of German measles (Rubella, caused by rubella virus) is extremely similar to that of Measles, however it causes low-grade fever which is much milder. The major concern with German measles is contraction by pregnant women, as rubella virus is teratogenic and can cause birth defects.

Hand foot and mouth disease (caused by Coxsackie or enteroviruses) produces painful vesicular lesions on the oral mucosa, palms and soles.

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This post was written by Omar Rifai