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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 cases (31%). The incidences of low platelet counts (<150 × 103/mm3) and positive but low C reactive protein concentrations (1–5 mg/dl) were 82.8% and 65.5%, respectively. Serum 2’-5’ oligoaenylate synthetase (2-5AS), an inducible enzyme known to be increased in viral infections1 were detectable (>222 pmol/dl)2in 45% of the infants. In most cases platelet counts were at their lowest (mean of 106 × 103/mm3) at the onset of exanthema, while white cells and C reactive protein gradually increased to reach a maximum two to four days after onset. Hyperbilirubinaemia was frequently seen, with 68.1% of the infants requiring phototherapy. No specific virus was isolated and no raised titre of IgM antibody specific for any virus was observed. No bacteria were detected in the blood culture. No major complication was observed in the term infants, but in preterm infants apnoea was sometimes seen, and two infants died as a result of mucosal damage in the bronchial trees and gastrointestinal tract.
Although this condition is very similar to enterovirus infection, there are several distinguishing features. First, onset was too early to be an enterovirus infection: although enterovirus infection can sometimes occur soon after birth in cases of vertical transmission, in our cases, this seemed to be transmitted horizontally after birth. Secondly, no virus was isolated from any samples in spite of extensive virological examination. Thirdly, thrombocytopenia has not been recognised as a common feature of enterovirus infection. We believe our patients had a new, unknown clinical syndrome.
Figures 1A and B Typical exanthema.
Many neonatologists have reported a similar condition in Japan, since we first reported this at the annual congress of the Japan Society of Neonatology in 1994. We sent out a questionnaire to 25 major hospitals in Japan and found that 27 cases had occurred in eight hospitals (out of 15) within the previous six months. This condition is therefore becoming a puzzling and increasingly important issue for neonatologists in Japan.
We think that an unknown virus or bacterial toxin may be responsible. It is unlikely to be caused by another kind of toxin or drug reaction, because it occurred mainly in infants who had been delivered normally and who had not received any special treatment. The disease usually regresses without any treatment or change in care.
It is important to determine if a similar condition has been observed elsewhere. We want to draw paediatricians’ attention to it and would be grateful to hear from others who have come across it, so that we can gather more information on it.