When a young actress shares her cancer journey on Instagram, it resonates far beyond Hollywood. Kelley Mack, best known for playing Addy on The Walking Dead, did exactly that—and on August 2, 2025, she died at age 33 from a rare brain cancer called diffuse midline glioma.
Age at death: 33 ·
Date of death: August 2, 2025 ·
Known for: Addy in The Walking Dead (season 9) ·
Cause of death: Diffuse midline glioma
Quick snapshot
- Exact date of diagnosis
- Specific treatment regimen details
- Full list of her film and voice credits
- Born July 10, 1992; died August 2, 2025 (ABC News)
- Diagnosed in 2024–2025 after lower back pain and shooting leg pains (ABC News)
- Family plans a remembrance service August 16, 2025 in Glendale, Ohio (ABC News)
- Another celebration of life in Los Angeles to be determined (ABC News)
Six facts about Kelley Mack, and one pattern: a young life cut short by a tumor that is usually diagnosed in children.
| Label | Value |
|---|---|
| Full name | Kelley Lynne Klebenow (Kelley Mack) |
| Born | July 10, 1992 |
| Died | August 2, 2025 |
| Age at death | 33 |
| Cause of death | Diffuse midline glioma |
| Known for | Role of Addy in The Walking Dead (season 9) |
What did Kelley Mack pass away from?
Cause of death confirmed as diffuse midline glioma
Kelley Mack died on August 2, 2025 at age 33, with her mother and aunt at her side, according to a family statement shared with ABC News (U.S. news outlet). The cause was diffuse midline glioma, a rare and aggressive brain cancer. Her family publicly announced her passing on Facebook and in news reports, noting that she died peacefully in Cincinnati.
Statements from family and news sources
In an Instagram post from January 2025, Mack described persistent lower back pain and shooting pains in her legs and back that preceded her diagnosis (ABC News). The Economic Times (Indian financial newspaper) reported that her death occurred in Cincinnati, surrounded by family. A recognition and remembrance service is planned for August 16, 2025 in Glendale, Ohio, with a later Los Angeles celebration to be announced.
Kelley Mack’s case challenges the assumption that diffuse midline glioma only strikes children; diagnosed at 33, she was a rare adult patient whose story brought public attention to an underfunded area of neuro‑oncology.
The pattern: her public timeline offers clinicians a rare window into how this pediatric tumor manifests in adults.
What kind of glioma did Kelley Mack have?
Diffuse midline glioma explained
Mack herself described diffuse midline glioma as an extremely rare type of astrocytoma cancer (ABC News). According to The Economic Times, these tumors grow in midline structures such as the brainstem, thalamus, and spinal cord. Their diffuse nature makes them almost impossible to surgically remove, and the cancer carries one of the worst prognoses among brain tumors.
How this glioma differs from other brain tumors
Most diffuse midline glioma cases are diagnosed in children. Mack’s diagnosis as a young adult underscores the disease’s unpredictable reach (The Economic Times). The exact causes remain unclear, and treatment options are limited—no cure exists, only palliative approaches to manage symptoms.
For the medical community, Mack’s public disclosure—from lower back pain to diagnosis—provides a rare patient timeline that may help clinicians recognize early signs of midline glioma in young adults.
What are the first signs of a glioma?
Common early symptoms include headaches, seizures, nausea, and cognitive changes. With diffuse midline glioma, because it grows in the brainstem, thalamus, or spinal cord, motor or sensory deficits—like the lower back pain and shooting leg pains Mack described—can be early clues. Anyone experiencing persistent neurological symptoms should seek medical evaluation.
The implication: early detection remains difficult, but recognizing atypical symptoms in adults is critical for timely diagnosis.
Who is Addy in The Walking Dead?
Addy’s role in season 9
Kelley Mack portrayed Addy, a member of the Hilltop community, during The Walking Dead season 9. Addy appears in the Whisperer arc—a storyline that introduced the masked, skin‑wearing antagonists. Her character was part of the group that encountered the Whisperers’ threat, and Mack’s performance was noted for bringing grounded emotion to a post‑apocalyptic drama.
Kelley Mack’s performance
Beyond The Walking Dead, Mack had a guest role on Chicago Med and pursued voice‑over and independent film work. Her IMDb credits include short films and television appearances, though a full list of her roles has not been widely compiled. The family has not yet released a complete filmography.
Who did Kelley Mack play on Chicago Med?
She appeared as a guest star in a single episode; the exact character name has not been widely reported. Her role came before her The Walking Dead appearance, highlighting her steady work as a working actor in major network series.
The takeaway: Mack’s career as a working actor in major network and cable series highlights the breadth of her craft, even though her most visible role was a brief but memorable part in one of television’s longest‑running dramas.
Fans who know her only as Addy may never see the full range of her work; but the intensity of that single role, set against her real‑life battle, gives Addy an unexpectedly poignant legacy.
What this means: her brief screen time belies a career built on versatility and quiet dedication.
Timeline
- July 10, 1992 – Kelley Mack born in Cincinnati, Ohio. (Family statement)
- 2010s – Acting career begins; guest roles on television, including Chicago Med. (IMDb)
- 2018–2019 – Portrays Addy in The Walking Dead season 9. (ABC News)
- 2024–2025 – Diagnosed with diffuse midline glioma; shares her journey on Instagram, describing lower back pain and shooting leg pains. (ABC News)
- August 2, 2025 – Kelley Mack passes away peacefully with family at her side. (ABC News)
- August 6, 2025 – News outlets report her death; family announces remembrance services. (ABC News)
The pattern: from diagnosis to death, the timeline underscores the aggressive nature of this rare cancer.
What’s confirmed, what’s unclear
Confirmed facts
- Kelley Mack died on August 2, 2025 at age 33 (ABC News)
- Cause of death was diffuse midline glioma (ABC News)
- She played Addy in The Walking Dead season 9 (ABC News)
- She was an actress and producer (ABC News)
What’s unclear
- Exact date of diagnosis
- Specific details of her treatment regimen
- Full list of her film and voice credits
The catch: the gaps in public records reflect the family’s desire for privacy during her illness.
In her own words and those who loved her
She passed away peacefully with her mother and aunt at her side.
— Family statement, via ABC News
Diffuse midline glioma is an extremely rare type of astrocytoma cancer.
— Kelley Mack, from her January 2025 Instagram post, as quoted by ABC News
Mack’s decision to speak openly about her diagnosis gave a human face to a little‑known disease. For fans of The Walking Dead, the loss is deeply personal; for the medical community, her story underscores the urgent need for research into diffuse midline glioma—a cancer that, even when caught early, offers little hope. The implication is clear: awareness alone won’t save lives, but it can drive the funding and focus that rare‑disease research desperately needs.
Frequently asked questions
How old was Kelley Mack when she died?
She was 33 years old. She was born July 10, 1992 and died August 2, 2025.
What is diffuse midline glioma?
A rare and aggressive brain cancer that grows in midline structures like the brainstem, thalamus, and spinal cord. It is difficult to surgically remove and has no cure.
Did Kelley Mack have children?
There are no public reports that she had children. Her family statement did not mention any.
What episode of The Walking Dead was Kelley Mack in?
She appeared in multiple episodes of season 9 as Addy, a member of the Hilltop community during the Whisperer arc. Specific episode numbers include season 9 episodes such as “Adaptation” and “Bounty.”
Was Kelley Mack married?
Her marital status has not been publicly disclosed. Family statements refer only to her mother and aunt.
How long did Kelley Mack have glioma?
She was diagnosed in 2024–2025, about a year before her death. The exact date is not public.
What other TV shows was Kelley Mack in?
She had a guest role on Chicago Med and smaller roles in independent films and voice-over work.
Each question reflects the public’s desire to understand the life and loss of a young actress who faced a rare disease with openness.
Related reading
- Rock Hudson: Death, AIDS Disclosure, Movies & Legacy – The story of another actor whose health battle reshaped public discourse.
- JJ Maybank: Real Name, Actor, and Death Explained – A guide to a fictional character’s tragic end, examined through real‑world loss.
Henry William Bennett Murray is a staff writer for CivicInsight.uk, covering UK public affairs, policy and civic life. He works under Editor-in-Chief Rebecca Langford, following the newsroom standards for sourcing, verification and fact-checking set out in our editorial policies.