Image copyright AP Image caption The Short family - seen here in 2014 - were featured in local news reports after Willow's (centre) heart transplant

A Pennsylvania couple, who struggled to find medication after their young daughter received a heart transplant, have been found dead along with their children in an apparent murder suicide.

Mark and Megan Short and their children, aged 8, 5 and 2, died of gunshot wounds, police said.

Police called the deaths a "tragic domestic incident."

The family was featured in news reports after Willow Short, then an infant, received a heart transplant in 2014.

Since then, the Shorts had trouble obtaining Willow's medication on time. The drugs that prevented Willow's body from rejecting her new heart are subject to strict rules, which often complicated their delivery.

The hurdles the family faced were detailed in a New York Times article.

Megan Short wrote in a blog that she suffered from Post Traumatic Stress Syndrome (PTSD) amid Willow's difficult treatments.

"I don't think PTSD ever truly goes away but, with therapy, medication, and the right support, I have begun to loosen its grip on me," she wrote.

"As I work on my own mental healing, I wanted to share my experience so that other heart parents know they are not alone."

Neighbours told the Reading Eagle that the couple had been heard arguing and Megan Short planned to leave her husband.

Authorities said they found a "murder-suicide" note and one of the adults was found with a handgun.