Idiopathic thrombocytopenic purpura (ITP) can occur after measles/mumps/rubella (MMR) immunisation, although its incidence is much lower than that after measles or rubella infection. MMR does not reactivate previous acute ITP.1 2 A second booster dose of MMR appears also to be safe in this regard.3 However, less is known about the safety of MMR in chronic ITP. We present three cases of children with chronic ITP whose illness was not exacerbated by immunisation (summarised in table 1).

In the first case, a girl was diagnosed at 13 months old after admission for a petechial rash with a platelet count of 5×10⁹/l. Despite trials of prednisolone, pulsed dexamethasone and intravenous immunoglobulins, her disease …