Socialite Kourtney Kardashian has wished her son, Mason, on his birthday by posting a photograph of him online.

"Happy birthday to my precious angel who has forever blessed my life. The happiness this boy brings me has no words to describe it," the 34-year-old posted with the photograph on Instagram, reports eonline.com.

The "Keeping Up With the Kardashians" star started her son's fourth birthday celebration with a fun trip to Disneyland.

Kourtney gave birth to Mason in December 2009 with her long-time partner Scott Disick. The couple also has a daughter, Penelope.