‘The Walking Dead’ Star Kelley Mack Dies Aged 33 From Rare Brain Cancer — Warning Signs You Should Never Ignore

What are the main symptoms of Kelley Mack’s brain cancer, diffuse midline glioma?

The entertainment world is grieving the loss of a talented actress whose light shone brightly, even in the face of a tough battle.

Kelley Mack, known for her role as Addy in The Walking Dead, passed away at just 33 years old.

Her story is one of strength, creativity, and a life cut short by a rare illness.

Let’s take a closer look at her journey, the disease she faced, and the legacy she leaves behind.

Who Was Kelley Mack?

Kelley Mack, born Kelley Lynne Klebenow in Cincinnati, Ohio, was a rising star in Hollywood. She captured hearts as Addy, a survivor in the Hilltop Colony, during season nine of The Walking Dead (2018–2019).

Her acting career didn’t stop there—she appeared in shows like Chicago Med as Penelope Jacobs and 9-1-1, and voiced Gwen Stacy in Spider-Man: Into the Spider-Verse. Kelley also starred in films like Broadcast Signal Intrusion (2021) and Mr. Manhattan (2024).

Beyond acting, she was a writer, director, and producer, showing her love for storytelling in every project. Her family described her as a warm, creative soul who loved hiking, playing piano, and spending time with her boyfriend, Logan, and her family.

Kelley Mack’s Brain Cancer: Raising Awareness for a Rare Tumor

In September 2024, Kelley shared that she had been diagnosed with diffuse midline glioma, a rare and aggressive brain cancer. This type of tumor starts in the brain or spinal cord and is hard to treat because of its location.

Kelley first noticed symptoms like lower back pain, which she thought was a slipped disc. Soon, she felt nerve pain, itching in her thigh, and severe leg and back pain that made lying down unbearable.

An emergency MRI in November 2024 found a mass on her spinal cord. After a biopsy, she lost the use of her right leg and most of her left, relying on a walker and wheelchair.

Despite these challenges, Kelley stayed positive, sharing updates about her recovery, like walking up stairs with Logan’s help in March 2025. She underwent proton radiation and physical therapy, but the cancer was too aggressive. Kelley passed away peacefully on August 2, 2025, with her mother, Kristen, and aunt Karen by her side.

Understanding Glioma and Its Challenges

Glioma is a tumor that forms when glial cells, which support the brain and spinal cord, grow out of control. Diffuse midline glioma, the type Kelley had, is especially rare, affecting only 200–300 people in the U.S. each year.

It’s most common in children and older adults, but it can strike anyone. Symptoms depend on the tumor’s location and may include headaches, seizures, vision problems, weakness, or trouble with balance and speech. Treatment is tough because the tumor’s position makes surgery risky, and the brain has a limited ability to repair itself.

Options include surgery (when possible), radiation, and chemotherapy, but high-grade gliomas like Kelley’s are often resistant. Risk factors include radiation exposure, genetic conditions, and, rarely, family history. Kelley’s openness about her illness helped raise awareness about this rare disease.

A Legacy of Light

Kelley’s family shared that she appeared to loved ones as butterflies after her passing, a touching symbol of her gentle spirit. Her The Walking Dead co-stars, like Alanna Masterson, and director Michael Satrazemis, praised her warmth and talent.

A memorial is planned for August 16 in Glendale, Ohio, with another celebration in Los Angeles, where Kelley lived for 11 years. Her final project, the comedy-drama Universal (2025), where she starred and served as an executive producer, showed her incredible spirit.

Kelley’s courage and creativity will live on through her work and the lives she touched.

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