Editor—Since 1992 we have observed many neonates who had exanthema and other features in common, including a high incidence of thrombocytopenia. We summarised the data from 29 infants admitted to our unit in Tokyo with this condition between November 1992 and July 1994. During this period, about 1300 infants were born in our hospital, and the incidence of this condition was about 2.5%. The typical exanthema, which is generalised erythema with a tendency to fuse, is shown in fig 1.

Exanthema appeared very early (a mean of 2.8 days) in life and usually disappeared three days after onset. Fever was observed before onset in nine …