The family of respected animal expert Jack Hanna announced that he has been diagnosed with dementia

The family of respected animal expert Jack Hanna announced that he has been diagnosed with dementia.

In a letter shared on Wednesday, his three children revealed that the 74-year-old wildlife aficionado who was known for his khaki zookeepers clothing and Indiana Jones style brown leather hat may have Alzheimer's disease.

Hanna was best known for bringing unusual animals on to the breakfast chat show Good Morning America as well as The Late Show With David Letterman.

Health update: The family of respected animal expert Jack Hanna announced that he has been diagnosed with dementia.In a letter shared on Wednesday, his three children revealed that the 74-year-old wildlife aficionado may have Alzheimer's disease. Seen in 2017

Almost 30 years ago: His day job was as Director Emeritus of the Columbus Zoo and Aquarium; seen in 1992

His day job was as Director Emeritus of the Columbus Zoo and Aquarium. 

'Today, we reach out to share some personal Hanna Family news,' his kids Kathaleen, Suzanne and Julie, said in a letter. 

'Doctors have diagnosed our dad, Jack Hanna, with dementia now believed to be Alzheimer's disease.' 

Family time: Here is a photo from his Facebook page with his wife since 1968 Suzi Egli and their three daughters Kathaleen, Suzanne and Julie

Some very early days: The family also posted this image of Jack and his kids from the Seventies

The heartfelt note: The letter got right to the point and then shared some touching anecdotes about Jack

And Terraristik Fachhandel his children added that the dementia has moved quickly.