"In this Dec. 23, 2013, file photo, former San Francisco 49ers wide receiver Dwight Clark is honored at halftime of an NFL football game between the 49ers and the Atlanta Falcons in San Francisco. Clark stands near the spot where he made a catch so famous it is referred to as ""The Catch.""  Clark says he has Lou Gehrig's disease and suspects playing football might have caused the illness. Clark announced Sunday, March 19, 2017. on Twitter that he has amyotrophic lateral sclerosis, a disease that attacks cells that control muscles. Clark linked to a post on his personal blog detailing his ALS diagnosis, but the site crashed Sunday night, apparently from an overflow of traffic.  Photo: Tony Avelar, Associated Press"