[Subacute sclerosing panencephalitis: fulminant form]. 
Subacute sclerosing panencephalitis (SSPE) has become less frequent as a consequence of massive anti measles vaccination.  Early infection or immunological factors could increase the risk of its appearing and of evolved forms of the disease.  We describe the cases of four patients with fulminating forms of SSPE: a girl who had measles at the age of eight months; a male who, without actually suffering the clinical disease, came into contact with measles in the family and, despite having been vaccinated, presented SSPE 18 months after the contact; a boy aged 4 years and 4 months who had measles at the age of 6 months, and a boy of a similar age who had the illness when he was one year old.  They all developed ataxia, with focal and generalised neurological signs, myoclonic and atonic seizures with rapid deterioration of language and the cognitive functions.  In the four cases, the computerised tomography scans were normal, the electroencephalograms showed bilateral paroxysms and periods of recurrent bioelectrical attenuation.  The magnetic resonance images of the four patients revealed disseminated hyperintense lesions, and one of the patients presented hyperintense lesions in the cervical spinal cord.  The anti measles IgG titres were high in the cerebrospinal fluid.  Anti convulsive drugs were ineffective.  In the third and fourth patients, intrathecal intraventricular treatment with interferon did not modify the course of the disease and neurological deterioration was seen in the subsequent follow up of all the cases.  As a consequence of vaccination against measles, SSPE has become less frequent.  Infection of infants, prior to the immunisation stage, can induce SSPE with periods of latency that are shorter than usual and with a fast progression of the disease.