One Year Later: Influencer Reveals Rare Brain Tumor Diagnosis Behind Daughter's Sudden Death

A year of waiting for answers ended in heartbreak and clarity for influencer Lizzie Kieffer. On May 16, she shared what she and her family finally learned about the sudden death of her daughter Lilian Louise, who passed away on April 23, 2025, just days before turning 2 years old.

The diagnosis: ATRT (Atypical Teratoid Rhabdoid Tumor), an extremely rare and aggressive brain tumor. It’s the kind of news that arrives too late to change anything—the tumor was located on Lily’s brainstem, and by the time testing confirmed it in October, months after her death, Kieffer and her husband Matt had already begun the impossible work of grieving. What makes Lily’s case particularly stark is how invisible the threat was. She showed no symptoms. She was taking her first steps just days before she died. That final morning, Kieffer fed her daughter a bottle while Lily giggled at her big sister Mia—a moment of ordinary joy that would become precious in a way no parent should ever know.

The medical picture, while grim, offers a kind of sorrowful comfort. Doctors believe a concurrent stomach bug and cold—common childhood illnesses—triggered enough inflammation in her brain to compromise her already fragile brainstem. Even if the tumor had been detected earlier, survival rates for ATRT in that location would have been“extremely, extremely low,”Kieffer explained while processing her loss publicly. Fewer than 100 cases of ATRT are diagnosed each year in the United States, making it devastatingly rare and impossibly hard to spot.

What Kieffer has chosen to do with her grief is use it as a lighthouse. She’s shared Lily’s story—and her diagnosis—to raise awareness about a disease most people have never heard of. She emphasized that the tumor was not genetic but a random mutation that occurred while Lily was developing in the womb. In her words, the family is“allowing the days that are so hard to be hard”while holding onto hope and the knowledge that Lily“passed in complete peace”without pain or suffering.

For Kieffer, Mia, and Isla, the journey forward means finding good in the grief, honoring Lily’s brief life, and trusting that her daughter’s story—and her legacy—will continue to matter. That’s the only leverage grief ever gives us: the chance to make meaning from loss, and to ensure that even the shortest lives leave a mark.