Denise Richards' youngest daughter has a rare chromosome disorder.

The 'Real Housewives of Beverly Hills' star - who has Sam, 14, and Lola, 13, from her marriage to Charlie Sheen and adopted seven-year-old Eloise as a lone parent - admitted she is ''learning every day'' because there isn't a ''road map'' for how to treat the youngster's condition, which has caused ''a lot of developmental delays''.

Denise told People magazine: ''She wasn't able to sit up on her own for a very long time, and she didn't start walking until she was two, and that was with physical therapy.

''She can only say a handful of words [now]. And there are times when she feels like her age in understanding, and then other times where it feels she's emotionally three years old. It's been challenging. I'm learning every day because they don't really have a road map for her particular case.''

Two and a half years ago, Eloise was diagnosed with a deletion in chromosome eight and though Denise - who married Aaron Phypers in September - doesn't know what the future holds for her daughter, she is staying optimistic.

She said: ''Every child is different You take care of your children no matter what is going on with them. I don't know if [Eloise] is ever going to talk like a typical child. But as a parent, you want what's best for your children, and you just do it.''

The 'World is Not Enough' actress' proudest achievement is the way she has raised her children, especially as they are growing up in very different circumstances to her own childhood.

She said: ''I'm most proud of raising my kids, especially in a time that is very different from how I was raised.

''It's extremely hard to keep children grounded. This is not an easy time to grow up.''