Hollywood has lost a bright star. Kelley Mack, best known for her role as Addy in The Walking Dead season nine, has passed away at just 33 years old after a courageous battle with a rare and aggressive form of cancer known as diffuse midline glioma.
Her family announced the heartbreaking news on Instagram, sharing that Mack “passed peacefully on Saturday evening” (August 2) with her mother, Kristen, and aunt, Karen, by her side. “Such a bright, fervent light has transitioned to the beyond,” they wrote, adding that loved ones have already felt her presence through butterflies—a touching symbol of her spirit.
A Rising Star Gone Too Soon
Mack’s acting résumé was impressive. Beyond The Walking Dead, she appeared as Penelope Jacobs in Chicago Med and made appearances in Fox’s 9-1-1. Her most recent role was in the drama-comedy Universal, alongside The Inbetweeners star Joe Thomas. Over her career, she earned 35 acting credits and also explored producing, with five projects to her name.
Kelley Mack as Addy and Matt Lintz as Henry in The Walking Dead (AMC)
Her co-stars have been quick to honor her memory. Alanna Masterson, who played Tara Chambler in The Walking Dead, wrote: “What an incredible human. So proud to have fought alongside her in our final episode together.”
Her Battle with Diffuse Midline Glioma
Kelley went public with her diagnosis last year. According to the National Cancer Institute (NCI), diffuse midline gliomas are fast-growing, grade-4 tumors that affect the brain or spinal cord. Mack first noticed persistent lower back pain in October 2024, which escalated to a hospital visit where doctors discovered a mass on her spinal cord.
Mack had completed proton therapy in March this year (Instagram/@itskelleymack)
Despite the grim prognosis, Kelley fought hard. She began proton therapy in January and completed 24 rounds by March, even undergoing tough physical therapy. She shared updates with her followers, writing that “things are getting better,” a testament to her resilience and hope.
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What Are the Symptoms of Diffuse Midline Glioma?
Symptoms vary based on the tumor’s location. According to the NCI, they may include:
- Double vision
- Difficulty swallowing
- Weakness or numbness in limbs
- Loss of balance
- Bowel and bladder control issues
More information is available on the NCI website.
Remembering Kelley
Kelley is survived by her parents, Kristen and Lindsay Klebenow; her siblings, Kathryn and Parker; her grandparents, Lois and Larry; and her boyfriend, Logan Lanier. Her family says her legacy will live on through her work and the countless lives she touched.
If you’ve been affected by similar health issues, you can contact the American Cancer Society at 1-800-227-2345 or via their 24/7 live chat for support.
