<prompt> Subacute Sclerosing Panencephalitis is a rare and dangerous complication of;MeaslesMumpsRubellaVaricella  <response>: SSPE Subacute sclerosing Pan encephalitis SSPE is a rare complication of measles. SSPE occurs in about 1 in every 300,000 natural cases of measles. It is a form of chronic progressive brain inflammation caused by slow infection with ceain defective strains of hypermutated measles virus It is also known as Dawsondisease,Dawsonencephalitis, andmeaslesencephalitis 