We have seen a number of patients who developed systemic exanthema and thrombocytopenia in the first week of life. Although nearly 100% of the patients were cariers of meticillin-resistant Staphylococcus aureus (MRSA), no clear link between MRSA and this exanthematous disease has yet been made.

20 neonates with exanthema and thrombocytopenia were selected for study. To see whether superantigenic exotoxins from MRSA are involved in the pathogensis of the exanthematous disease, we studied the production of these exotoxins by MRSA isolates from the neonates. We studied the expression of T-cell-receptor Vβ and CD45RO in T cells taken from four of the neonates. We also analysed the DNA sequences of 16 cloned Vβ2-positive T-cell-receptor-chain genes taken from two of the neonates.

Although most of the patients recovered within 5 days of onset of the exanthematous disease without any active treatment, two preterm infants died in the recovery phase. All patients showed colonisation by MRSA. The MRSA produced toxic shock syndrome toxin-1 (TSST-1). The number of T cells positive for T-cell-receptor Vβ2, reactive to TSST-1, was increased in the four patients studied (p<0·0001), and these T cells expressed CD45RO (p=0·0185). None of the Vβ2 clones had the same junctional sequences.

The polyclonal expansion of Vβ2-positive T cells in patients colonised by TSST-1-producing MRSA suggests that the pathogenic micro-organism of this neonatal exanthematous disease is S aureus, mainly MRSA, and that in its pathogenesis it activates T cells by TSST-1. Although the pathogenesis of both this exanthematous disease and toxic shock syndrome are fundamentally the same, a diagnosis of toxic shock syndrome cannot be made in this case, based on the clinical criteria for toxic shock syndrome. We propose neonatal toxic-shock-syndrome-like exanthematous disease (NTED) as the name for this disease.