Jack Osbourne has been diagnosed with multiple sclerosis.

The 26-year-old son of Sharon and Ozzy Osbourne and his fiance Lisa Stelly welcomed daughter Pearl in April.

Jack learned of his illness, which is a disease that adversely affects the central nervous system, just two weeks after Pearl was born.

The star felt awful about the news and felt the timing made the matter worse.

"I was just angry and frustrated and kept thinking, 'Why now?' " Jack told People magazine. "I've got a family and that's what's supposed to be the most important thing."

Damaging nerve cells in the brain and spinal cord, multiple sclerosis is often a progressive disease. The symptoms include loss of muscle control, adverse effects on balance and vision, feeling and thinking impairments.

The severity of the symptoms have a wide range, as some people with multiple sclerosis develop mild problems while others grow extremely disabled.