Selma Blair Sings Summer Camp Song with Fan

Selma Blair's zest for life is fully intact as she adjusts to life with multiple sclerosis ... which she made perfectly clear when she ran into a fan and started singing her heart out.

Selma was out in L.A. Thursday, enjoying a cup o' joe after leaving a beauty salon, when a young fan approached. Not just any fan, mind you -- the woman recognized the actress and said they'd gone to the same summer camp in Michigan. What happened next was ... pure joy.

It's great to see Selma smiling and laughing after recently opening up about her MS diagnosis with Robin Roberts. It's an unpredictable and often disabling disease of the central nervous system, and it can cause chronic problems with vision, muscle control and balance.

While MS can make even the most basic tasks nearly impossible -- Selma's not letting her condition dampen her spirits.