HealthDay LINK FOR FULL ARTICLEDetailed reports shed new light on why three patients who were treated with the biologic drug Tysabri for either multiple sclerosis or Crohn's disease developed severe brain infections.

In three scientific briefs and two editorials released Thursday by the New England Journal of Medicine, the specifics of each case are laid out and analyzed by experts in the field. The journal released the package early after a possible fourth case was reported last week. Two of the first three patients have died.

"This is the first time we've had a peer-reviewed report of the information provided by the company to the public," said Dr. John R. Richert, vice president for research and clinical programs for the Multiple Sclerosis Society. "It is the first time we have been able to peruse details of the cases."

Although the news of the infections first came as a blow to those in the MS community, Richert noted that some of the details in these case reports leave open the possibility that Tysabri might one day return to the market if screening methods are found to detect which patients might be susceptible to the brain infection.