Biogen Idec and FDA notified healthcare professionals that severe cutaneous or mucocutaneous reactions, some with fatal outcome, that have been reported in association with the Zevalin therapeutic regimen in the post-marketing experience. Patients experiencing a severe cutaneous or mucocutaneous reaction should not receive any further components of the Zevalin therapeutic regimen and should seek prompt medical evaluation

The reactions were reported in patients treated with the approved Zevalin regimen, which includes Rituxan, a drug sold by Biogen Idec and Genentech, according to a letter from Biogen Idec to doctors.

The letter further added that similar skin reactions have been reported previously with Rituxan

"The potential risk of these reactions should be considered when using the Zevalin therapeutic regimen," the company said in a letter to doctors.