Bernie Mac's widow is blaming her husband's death on the comedian's old dermatologist -- claiming the doc could have saved Bernie if he knew what he was doing.
According to docs filed last week in a Chicago Circuit Court -- Rhonda McCullough claims Dr. Rene Earles had a chance to save the comedian during a routine checkup ... but "failed to recognize and act upon abnormal vital signs and signs of respiratory failure."
According to the docs, McCullough claims Earles failed to properly diagnose Bernie with pneumonia and send the comic to the hospital ... and according to her, the mistake directly led to the funnyman's death in August 2008.
Earles told the Chicago Sun-Times it ain't his fault -- he claims Bernie had a bad allergic reaction to another doctor's injection once the comedian was hospitalized.
McCullough wants at least $50,000 in damages in the wrongful death suit.