The Teen Mom star breaks down in tears over her daughter's "pain," while Ali's twin, Aleeah, urges her sister -- who has muscular dystrophy ... to using her wheelchair. First, Leah sat down ...

The 32-year-old is raising three girls as a single mother ... parent argue with Aliannah, who has muscular dystrophy, over the importance of using her wheelchair. However, Aliannah passionately ...

Columnist Betty Vertin has a day of heightened awareness about her sons' experience with wheelchairs and life with DMD.

Ali, who lives with muscular dystrophy, tells her mom that she understands her own body's needs. "I don't need to [use the wheelchair.] If I don't need to, then I'm not going to," the teen says.