Danny Bonaduce is suffering from a "mystery illness".
The 62-year-old actor - who is best known for his childhood role as Danny Partridge on classic 1970s sitcom 'The Partridge Family' - caused concern to fans earlier this week when he announced he was taking "temporary medical leave" from his morning radio show and now his sister Celia has revealed that doctors are trying to figure out the problem as she thanked well-wishers for their support.
She wrote on Facebook: "Many of you have reached out to see what's going on with my brother Danny. Thank you. Along with Dairy Queen dipped cones and your messages, he is feeling the love. We are not being coy when we say this is a 'mystery illness.
"In layman's terms, his balance sucks- super sucks. All the great medical minds of Seattle are at work trying to solve this conundrum."
Celia concluded her posts by reminding fans that while Danny may be a "public figure" he is still just her "well-loved brother."
She added: "We will keep you posted. Please remember, that while he is a public figure, he is also my well-loved brother. Type your comments accordingly."
Following the statement, Danny himself took to Twitter to thank fans for their support and claimed that it "means a lot" that people had reached out.
He wrote: "Thank you for all of the well wishes. It really means a lot to me that so many of you have reached out. Just wanted to share something my sister posted on Facebook."
Just days earlier, Danny revealed that he was now using a walking stick, as he joked that he had joined a "cool club" along with Wily Wonka and Charlie Chaplin.
He tweeted: "Charlie Chaplin, Willy Wonka, Danny Bonaduce. I’ve joined the club of cool guys with canes!"