One of Mets catcher Landon Powell's 5-month-old twin daughters died on Friday night, the family announced on Saturday through its Facebook page.

Izzy Powell was battling hemophagocytic lymphohistiocytosis (HLH), a rare disease in which the immune system attacks vital organs. With her bone marrow and liver affected, Izzy underwent chemotherapy, but needed to grow more before she could receive a necessary bone-marrow transplant, the family said.

"Izzy went to be with her creator yesterday evening," Landon Powell and his wife, Allyson, wrote Saturday as part of a message on their Prayers for Izzy page. "She fought until the end and squeezed my hand tight until she left. My heart is broken, but I am blessed to know she is healthy and whole in heaven. I like to think she is twirling around and singing."

Besides Izzy's twin sister, the couple also has a son.

The Mets, who signed Powell to a Minor League contract earlier this month, released a statement via Twitter.

"The Mets family extends their condolences to Mets catcher Landon Powell and his wife, Allyson, on the loss of their daughter, Izzy," the club said.

Powell was a first-round pick by the A's in the 2004 First-Year Player Draft and spent parts of three seasons in the big leagues with Oakland from 2009-11. He played with the Astros' Triple-A Oklahoma City affiliate last year.