Rob Kardashian skipped his high school reunion, and on Instagram, his sister Kim put him on blast.

Rob Kardashian Looks Bigger Than Ever During Late-Night In 'N Out Visit

Following the release of new photos, which featured the reality star at what appears to be his heaviest, Rob opted out his his reunion, choosing to instead remain in hiding.

"Just received this pic from my brothers BFF from their 10 year high school reunion," Kim told fans, along with a photo of a letter from Rob written years ago. "It's a letter Rob wrote to himself back in high school. I wonder what it says. Rob can't remember either lol We're dying to read it together. I remember writing a letter like this before I graduated & projected where I would be in 10 yrs! I never went to see what it says! LOL 20yr?"

Is Rob Kardashian's Weight Gain Jeopardizing His Health?

In photos taken earlier this month, and shared by the UK's Daily Mail, Rob looked nearly unrecognizable as he made a late-night stop at a Los Angeles In 'N Out. After exiting his white Range Rover SUV, the reality star was spotted in a black t-shirt and matching shorts.

During a recent episode of Keeping Up With The Kardashians, Rob's mother, Kris Jenner, expressed her concern for her son.

'If I don't help him do something drastic, he's going to die," Jenner told Kim. "I'm just waiting for this horrible thing to happen and there's nothing we can do about it."

Keeping Up With The Kardashians season 10 airs Sundays at 9 p.m. on the E! Network.