Biogen Idec’s healthy financials for the third quarter have been overshadowed somewhat by confirmation that a patient on the oral multiple sclerosis blockbuster Tecfidera suffered from the rare viral brain infection associated with another of the company’s MS drugs Tysabri.

Biogen noted that a patient suffered from progressive multifocal leukoencephalopathy had been treated with Tecfidera (dimethyl fumarate) for four and a half years. The patient subsequently died from pneumonia but the company noted that the individual had been suffering from severe lymphopenia, abnormally low level of white blood cell condition, for over three years.

The news led to a 5.4% decline in Biogen’s share price to $309.07, despite the biotech posting a 37% rise in revenues to $2.51 billion and net income of $857 million (+76%). Tecfidera brought in $787.1 million, up from $286.4 million a year earlier but a bit lower than analyst estimates.

Its older MS drug Avonex (interferon beta-1a) inched up 1.1% to $741.8 million, while Tysabri (natalizumab) contributed $501.2 million, up from $401 million for third-quarter 2013.