YouTube star Caleb Bratayley's cause of death revealed

NEW YORK – The family of a young YouTube star who died unexpectedly last month has revealed what killed the 13-year-old.

Caleb Logan Bratayley died from a heart condition called hypertrophic cardiomyopathy, his mother said in an Instagram post Tuesday.

“Caleb didn’t have any symptoms so the doctor said there was nothing we could have done differently,” she wrote.

His two younger sisters – who also star in their family’s wildly successful YouTube videos – recently visited the doctor and their hearts “thankfully look the way they should right now,” their mother added.

Hypertrophic cardiomyopathy is usually inherited and causes the heart muscle to thicken, forcing the organ to work harder to pump blood, according to the U.S. National Institutes of Health. Though it can affect a patient at any age, the condition is likely to be more severe in younger patients, according to the NIH.

A patient with the condition may never notice any symptoms and sometimes the first sign of something wrong is sudden collapse and possible death, according to the NIH.

Initially, Caleb’s family said he’d died of “natural causes” but did not elaborate.

The Bratayley clan first began posting videos of their daily life some five years ago and have since amassed a fan base of nearly 2 million YouTube subscribers. Their videos have been watched more than 1 billion times.

Caleb had his own YouTube channel on which he would post videos about the game Minecraft. His final video was a message to his “future self.”

Since Caleb’s sudden death, the family has continued to put out new videos – all of which are accompanied by a caption that reads, “We will continue to grieve and miss Caleb everyday but we will not show it in the videos often. We have decided to honor him and continue this channel as it was intended, to be a celebration of life.”