Gunnar Peterson is asking for prayers as he reveals that his 4-year-old daughter, Monroe Vivian Peterson, has been diagnosed with acute myeloid leukemia.
The celebrity trainer shared the news March 27 on Instagram, explaining that Monroe's diagnosis came on the heels of symptoms that seemed like everyday "kid stuff" like a cough and fever.
"Our perfect 4 year old daughter, Monroe Vivian Peterson (MVP, see that?!) had a nagging cough, on and off fever, and an odd pallor to her for a few days last week. Typical kid stuff," Gunnar Peterson wrote alongside pics of little Monroe in her hospital bed surrounded by her family.
Peterson said his wife, Jess Peterson, later "noticed bruising" on Monroe's legs "which was odd since she hadn’t been very active because of the other symptoms" and took Monroe to the hospital.
"Fast forward 4 days," Gunnar Peterson continued, listing concerning results from Monroe's lab work: "White blood cell count KO’d. Platelets in the toilet. Hemoglobin number lower than a soccer game final. Hematocrit front row on the struggle bus."
He followed that by listing the intense treatment protocol that Monroe's physicians laid out for her: "Needs immediate transfusion(s). Has to have bone marrow biopsy. Flow cytometry. Spinal tap(s). Chemotherapy," he wrote.
The emotional dad added that his daughter had now become a “Make-A-Wish candidate.”
"AML leukemia. How the f*#! did we get here?!?!" he asked.
Acute myeloid leukemia is a type of cancer that starts in the blood-forming cells of the bone marrow, often progressing rapidly into the blood, according to the American Cancer Society.
AML can sometimes spread to other parts of the body including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles.
Peterson, whose celebrity fitness clients include reality star Khloe Kardashian and singer-actor Jennifer Lopez, expressed optimism about Monroe's prognosis.
"Our Warrior Princess will crush this! She has even said it herself!" he wrote before asking friends and fans for their support during the family's "nightmare."
"Please hold our daughter, and our family-immediate and extended-in your hearts, thoughts, and prayers. As we are all aware; ‘you never know what someone is going through,'" he wrote.
Peterson concluded his post by expressing his gratitude to his wife and other loved ones, as well as to two Tennessee-based hospitals, the Monroe Carell Jr. Children’s Hospital at Vanderbilt in Nashville and the St. Jude Children’s Research Hospital in Memphis.
Peterson signed off by writing, "Into the storm."
Dozens of Peterson's Hollywood friends rallied for him and his family in the comments of his post.
"We’re always here brother. Always. She will crush this, as she herself has declared," wrote Dwayne "The Rock" Johnson.
"Praying for Monroe and quick healing. We love you and your family so much Gunnar," wrote Emma Heming Willis, wife of actor Bruce Willis.
"G! Oh my heart!! I am so so so sorry for you and your family!! If there’s something I can say for certain, she’s a warrior just like her mommy and daddy!! G I’m here if you need anything! I love you and your family and im praying for you all!" wrote Khloe Kardashian.
Kardashian's sister Kim Kardashian and mom, Kris Jenner, were also among those who let Peterson know he and his daughter were in their hearts.
"My family and I are praying for your baby G we love you all so very much and lifting her up in the name of Jesus…." wrote Jenner.