Ms. Flack has been diagnosed with ALS, and is no longer able to sing.

How horrible.

TMZ has more.

In part:

The announcement came down Monday through the Grammy-winning singer's rep, who explained Roberta has difficulty even speaking these days due to her condition. No word on how long she's been suffering with ALS ... often known as Lou Gehrig's disease.

ALS breaks down a person's nerves over time and significantly deteriorates their functionality, especially as it pertains to muscle use. It has proven fatal, with no known cure.