Few things hit harder than hearing that a young actor whose face we welcomed into our living rooms is gone far too soon. Kelley Mack, known for her roles in The Walking Dead, Chicago Med, and 9‑1‑1, passed away on August 2, 2025, at age 33 after a battle with diffuse midline glioma — a rare and aggressive brain tumor. Her family confirmed the cause of death, and this article looks back at her career, the disease that took her, and what we know so far.
Full name: Kelley Lynne Klebenow · Born: July 10, 1992 · Died: August 2, 2025 (age 33) · Known for: The Walking Dead, 9‑1‑1, Chicago Med
Quick snapshot
- Diffuse midline glioma (ABC News)
- Rare and aggressive brain tumor (The New York Times)
- Passed peacefully on August 2, 2025 (ABC News)
- Diffuse midline glioma is a grade 4 tumor (Jackson Health System)
- Primarily affects children and young adults (ABC News)
- Symptoms include balance issues, headaches, nausea (TODAY)
Seven key facts, one pattern: each piece of information points to a talent lost much too young.
| Fact | Value |
|---|---|
| Full Name | Kelley Lynne Klebenow |
| Birth Date | July 10, 1992 |
| Death Date | August 2, 2025 |
| Age at Death | 33 |
| Known For | The Walking Dead, 9‑1‑1, Chicago Med |
| Notable Roles | Addy (The Walking Dead), Molly (Chicago Med) |
| Cause of Death | Diffuse midline glioma |
What Did Kelley Mack Pass Away From?
The Official Cause of Death
- Kelley Mack died from diffuse midline glioma, a rare brain cancer (ABC News).
- Her family announced her death on Instagram, writing: “It is with indelible sadness that we are announcing the passing of our dear Kelley.” (ABC News)
- The New York Times described the tumor as “aggressive” and located in the central nervous system (The New York Times).
Understanding Diffuse Midline Glioma
- Diffuse midline glioma is a rare subtype of glial tumor that starts in the brain or spinal cord (ABC News).
- Jackson Health System calls it “a rare and aggressive tumor affecting the central nervous system” (Jackson Health System).
- The National Cancer Institute estimates about 3,940 people live with diffuse midline gliomas in the U.S., with a relative five‑year survival rate of 42.2% (ABC News).
The implication: even with treatment, the odds are steep — making Mack’s public battle all the more poignant.
For fans and families facing a similar diagnosis, Mack’s story puts a face on a cancer that receives far less attention than more common tumors.
What Was Kelley Mack Diagnosed With?
Diagnosis Timeline
- Kelley Mack publicly said in January 2025 that she had been diagnosed with diffuse midline glioma (ABC News).
- An emergency MRI on November 4, 2024 found an abnormal mass on her spinal cord (TODAY).
- She later said biopsy surgery affected her spinal cord and resulted in loss of use of her right leg and most of her left leg (TODAY).
- By April 2025, she had completed proton radiation treatment (Wikipedia).
What Is Diffuse Midline Glioma?
- It is a grade 4 brain tumor according to the World Health Organization classification (Jackson Health System).
- Common symptoms include headaches, nausea, vomiting, and balance problems (TODAY).
- It tends to occur in the thalamus, brainstem, or spinal cord, making surgical removal extremely difficult (The New York Times).
What this means: the location and aggressive nature of this tumor present treatment challenges that most patients and their families cannot prepare for.
Who Did Kelley Mack Play on Chicago Med?
Character: Molly in Chicago Med
- She played a character named Molly in an episode of Chicago Med season 9 (YouTube).
- The role was a guest appearance, adding to her portfolio of medical‑drama credits (TODAY).
Other TV Roles
- She is best known for playing Addy in The Walking Dead season 9 (ABC News).
- Her 9‑1‑1 appearance was also a guest role (TODAY).
- For readers interested in similar stories of young actors lost to cancer, see Jonathan Brown’s Brain Tumour and Sage Stallone Cause of Death.
The pattern: each role, though often brief, left an impression on audiences who now seek to understand the person behind the character.
Who Was Kelley Mack on 9‑1‑1?
Character in 9‑1‑1
- Mack appeared in an episode of 9‑1‑1 in 2023, though her character’s name has not been widely published (TODAY).
- The role added to her growing résumé of high‑profile network dramas (People).
Impact of Her Role
- While a small part, it demonstrated the breadth of her acting range — from zombie horror to first‑responder drama (TODAY).
- Fans have since revisited her scenes to honor her memory (People).
The catch: the brevity of some roles belies the dedication she brought to each performance.
What Are the Symptoms of Kelley Mack’s Glioma?
Common Symptoms of Diffuse Midline Glioma
- Typical symptoms include headaches, nausea, vomiting, and difficulty with balance and walking (TODAY).
- Because the tumor often grows in the brainstem or spinal cord, symptoms can also involve double vision, facial weakness, and trouble swallowing (Jackson Health System).
How Symptoms Progressed
- Mack herself described persistent lower back pain and shooting pains before her diagnosis (ABC News).
- After surgery she lost the use of her right leg and most of her left leg (TODAY).
- Her representative told People that her death was “very unexpected” despite the cancer battle (People).
The trade-off: aggressive treatment can extend life but often at the cost of severe neurological deficits.
Mack’s openness about her symptoms and treatment gives the public a rare, unfiltered look at what living with diffuse midline glioma really means.
Timeline signal
- July 10, 1992 – Born in Cincinnati, Ohio (Wikipedia)
- Late 2010s – Begins acting career with minor roles (ABC News)
- 2018–2019 – Plays Addy in The Walking Dead (season 9) (ABC News)
- 2022 – Appears in Chicago Med as Molly (YouTube)
- 2023 – Guest role in 9‑1‑1 (TODAY)
- November 4, 2024 – Emergency MRI finds spinal cord mass (TODAY)
- January 2025 – Publicly announces diffuse midline glioma diagnosis (ABC News)
- August 2, 2025 – Dies at age 33 (ABC News)
Confirmed facts
- Cause of death: diffuse midline glioma (ABC News)
- Birth date: July 10, 1992 (Wikipedia)
- Death date: August 2, 2025 (ABC News)
- Roles in The Walking Dead, Chicago Med, 9‑1‑1 (ABC News; TODAY)
What’s unclear
- Exact date of her diagnosis (ABC News)
- Specific symptoms she personally experienced beyond back pain and leg weakness (TODAY)
- Whether she had any additional prior health conditions (People)
Quotes From Those Close to Her
“It is with indelible sadness that we are announcing the passing of our dear Kelley.”
Family statement via Instagram, reported by ABC News
“Her death was very unexpected, despite her cancer battle.”
Mack’s representative, reported by People
The pattern: those who knew her describe a fighter whose sudden decline took everyone by surprise.
For her family, the loss is immeasurable. For the medical community, her story reinforces the cruel unpredictability of diffuse midline glioma. And for the audience who watched her on screen, the takeaway is sharp: a young talent taken before her prime, leaving behind a body of work that now carries an even deeper weight. For fans and readers in the U.S., the choice is clear: remember her by watching her scenes, learning about the disease, or supporting brain‑cancer research — or let her story fade into the noise.
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Frequently asked questions
Did Kelley Mack have children?
No public information indicates she had children.
Was Kelley Mack married?
She was not married at the time of her death, according to available records.
What was Kelley Mack’s net worth?
Her net worth has not been publicly disclosed.
Where is Kelley Mack buried?
Burial details have not been made public by her family.
What other movies did Kelley Mack appear in?
Beyond her TV roles, she did not have major movie credits.
Did Kelley Mack have any siblings?
Her family statement did not mention siblings, and no sibling information is publicly available.
What was Kelley Mack’s education background?
Her education history has not been widely reported.
James Mitchell is Editor-in-Chief at Southern Monitor, overseeing editorial standards, publication decisions and corrections.