exanthems

The numbered list remains a useful framework. First disease is measles (rubeola), with the three Cs, Koplik spots as the enanthem, and a descending confluent maculopapular rash. Second disease is scarlet fever from group A Streptococcus, with a sandpaper rash, strawberry tongue, and desquamation. Third disease is rubella, with a milder descending rash and tender posterior auricular and suboccipital lymphadenopathy, dangerous chiefly in pregnancy. Fourth disease, staphylococcal scalded skin syndrome, is of historical interest. Fifth disease is erythema infectiosum from parvovirus B19, with slapped-cheek facial erythema followed by a lacy reticular rash on the limbs, arthralgia in adults, aplastic crisis in haemolytic disease, and hydrops fetalis in pregnancy. Sixth disease is roseola infantum from HHV-6, in which three to five days of very high fever, sometimes with a febrile seizure, is followed by defervescence and only then a rose-pink rash. Other important exanthems are varicella, with lesions in different stages simultaneously, and hand-foot-and-mouth disease from coxsackievirus A16.