Hollywood and fans of The Walking Dead are mourning the loss of actress Kelley Mack, who passed away on August 2, 2025, at the young age of 33 after a courageous battle with glioma, a rare and aggressive brain and spinal cord cancer.
Mack, best known for playing Addy in Season 9 of the hit AMC series, revealed her diagnosis earlier this year in an emotional Instagram post. She shared that what she initially thought was a simple slipped disc turned out to be diffuse midline glioma—a rare form of cancer that affects the central nervous system.
From Back Pain to a Life-Changing Diagnosis
Kelley Mack first experienced persistent lower back pain in September last year. At first, she believed it was due to an injury. But when the pain spread to her legs and became unbearable, she was forced to sleep in a recliner for weeks.
An emergency MRI revealed an abnormal mass on her spinal cord. Doctors diagnosed her with diffuse midline glioma, a fast-growing tumor known for its poor prognosis.
“Such a bright, fervent light has transitioned to the beyond,” her family shared on Instagram, confirming her passing.
What is Diffuse Midline Glioma?
According to the National Cancer Institute, diffuse midline glioma (DMG) is an aggressive tumor that develops in the brainstem, thalamus, or spinal cord. It can occur in both children and adults.
A common marker for DMG is a mutation in the histone H3 gene (H3 K27M), which plays a role in tumor growth.
Symptoms may include:
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Severe headaches (often worse in the morning)
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Nausea and vomiting
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Memory loss or confusion
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Mood and personality changes
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Vision problems
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Seizures
If you notice these symptoms persist, early medical evaluation is crucial.
Kelley Mack’s Courage and Career
Born Kelley Lynne Klebenow in Cincinnati, Ohio, Mack’s love for storytelling began in childhood. She went on to earn 35 acting credits and 5 producing credits, with appearances in Chicago Med, 9-1-1, indie films, commercials for Dr. Pepper and Chick-fil-A, and voice work in the Oscar-winning Spider-Man: Into the Spider-Verse.
She was also a writer, working on a baseball-inspired film script with her mother, based on their family history. Her brother, Parker Mack, is also an actor, and the siblings inspired each other creatively.
Tributes From Hollywood & Fans
Co-stars and friends remembered Kelley as “gifted,” “extraordinary,” and “a kind soul” who radiated positivity on and off set. Fans flooded social media with messages, sharing how her performances touched their hearts.
Her family shared that in her final days, butterflies—a symbol of transformation and hope—appeared to loved ones, giving them comfort that Kelley’s spirit lives on.
Final Goodbye
Kelley Mack’s memorial service will be held on August 16, 2025, at the Glendale Lyceum in Glendale, Ohio, with another celebration of life planned in Los Angeles.
Her legacy—as an actress, storyteller, and compassionate human being—will continue to inspire.
Rest in peace, Kelley Mack. Your light, talent, and kindness will never be forgotten.
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