LATEST: Shock jock HOWARD STERN's former radio sidekick KENNETH KEITH KALLENBACH's death was caused by complications from cystic fibrosis, according to a new medical examiner's report.

Kallenbach - described by Stern as the "ultimate airhead" - died in April (08) at the age of 39 at a Pennsylvania hospital.

Kallenbach was in custody at Delaware County Jail after being arrested and charged with attempted child abduction when he fell ill.

His initial cause of death was disputed by his mother Fay Kallenbach, who refuted claims her son had contracted pneumonia in jail.

Fay broadcast her concerns on Stern's Sirius Satellite radio show following Kallenbach's passing, insisting her son suffered from cystic fibrosis and wasn't properly cared for behind bars.

County officials disputed allegations of neglect, but autopsy reports have revealed the cause of death was attributable to the potentially fatal condition, which affects the lungs and digestive system.