‘The Walking Dead’ Actress Kelley Mack Dies at 33 After Battle with Rare Central Nervous System Cancer

In heartbreaking news for fans and the entertainment industry, actress Kelley Mack, widely recognized for her role as Addy in season nine of The Walking Dead, has died at the age of 33. Mack passed away on August 2, 2025, following a courageous battle with diffuse midline glioma—a rare and aggressive form of cancer that affects the central nervous system.

Her family confirmed that she died peacefully surrounded by loved ones, including her mother and aunt. Known for her bright spirit and creative energy, Mack’s passing has left an indelible mark on her peers and fans alike. In a heartfelt family statement, she was described as “a bright, fervent light” who will be deeply missed.

What Is Diffuse Midline Glioma and How Does It Affect the Central Nervous System?

Diffuse midline glioma is a rare, fast-growing type of tumor that forms in the brain or spinal cord. Classified as a subtype of glial tumors, it targets crucial areas in the central nervous system (CNS), making treatment particularly challenging. According to data from the National Cancer Institute, this aggressive cancer affects an estimated 3,940 individuals in the U.S., with symptoms that may include:

• Lower back pain

• Leg weakness or paralysis

• Vision problems

• Difficulty swallowing

• Imbalance and loss of coordination

In Kelley Mack’s case, the cancer initially presented through persistent back pain and sharp leg pains. A subsequent biopsy confirmed the diagnosis of diffuse midline glioma, a rare astrocytoma variant. Tragically, complications from spinal cord surgery left her wheelchair-bound, yet she remained determined to share her journey through personal posts and public advocacy.

Kelley Mack’s Career: From ‘The Walking Dead’ to Indie Horror Films

Mack’s acting career was marked by diverse roles across TV and film. Beyond her memorable portrayal in The Walking Dead, she also appeared in NBC’s Chicago Med as Penelope Jacobs and in the psychological horror film Broadcast Signal Intrusion. A graduate of Chapman University in 2014, Mack built her career in Los Angeles, working not only as an actress but also as a writer, producer, and voiceover artist.

Born Kelley Klebenow in Cincinnati, Ohio, she spent her early years across Ohio, North Carolina, and Illinois. She was the eldest of three siblings, including actor Parker Mack.

Her family has announced that a public remembrance ceremony will be held on August 16 in Glendale, Ohio, with a second event in Los Angeles scheduled at a later date.

Why It Matters: Glioma Awareness and Young Adult Cancer

The loss of Kelley Mack brings national attention to the devastating impact of rare cancers like diffuse midline glioma, especially among young adults. While it’s a relatively uncommon diagnosis, the cancer’s aggressive nature and resistance to treatment options demand urgent awareness and research funding.

Medical experts emphasize early detection and symptom awareness as vital tools in managing such rare CNS conditions. With only a 42.2% five-year survival rate, according to the National Cancer Institute, there’s a pressing need for advancements in treatment protocols—including experimental therapies and genetic-based research.

Expert Insight on Central Nervous System Tumors

Diffuse midline gliomas are especially challenging due to their location in sensitive brain and spinal cord regions. Dr. Elizabeth Maher, a clinical researcher in neuro-oncology, notes, “These tumors don’t just grow; they infiltrate. That’s what makes them so dangerous—and so difficult to treat surgically.”

Treatment options may include radiation therapy, chemotherapy, and emerging molecular-targeted medications. However, outcomes often depend on tumor location, patient age, and overall health.

A Legacy Beyond the Screen

Kelley Mack’s openness about her cancer journey has helped destigmatize disability and illness in the entertainment industry. Her family shared that since her passing, loved ones have reported seeing butterflies—a symbol they now associate with her enduring spirit.

Her resilience, creativity, and emotional honesty made her a role model both on and off the screen. Fans and colleagues continue to express their admiration and grief through social media tributes and private memorials.

Kelley Mack’s legacy now lives on not just through her performances, but through the greater awareness she brought to the realities of living with a central nervous system cancer like diffuse midline glioma.

You Must Know:

What is diffuse midline glioma?
Diffuse midline glioma is a rare, aggressive cancer that develops in the brain or spinal cord, commonly affecting children and young adults. It’s classified as a glial tumor and has a poor prognosis due to its inoperable location.

How did Kelley Mack die?
Kelley Mack died on August 2, 2025, from complications related to diffuse midline glioma, a rare cancer of the central nervous system. She was 33 years old.

What are the symptoms of central nervous system gliomas?
Symptoms may include severe back pain, muscle weakness, balance issues, visual disturbances, and partial paralysis, depending on the tumor’s location within the CNS.

What roles was Kelley Mack known for?
She was best known as Addy in The Walking Dead and also starred in Chicago Med and the horror film Broadcast Signal Intrusion.

Can diffuse midline glioma be cured?
Currently, there is no known cure. Treatment typically involves radiation, chemotherapy, and supportive care. Research is ongoing for targeted therapies.

Where will Kelley Mack’s memorial services be held?
Her family announced a remembrance service in Glendale, Ohio on August 16, and a second celebration in Los Angeles will be scheduled.