She played Addy, a quiet Hilltop colonist who barely made it through Season 9 of The Walking Dead. Off-screen, Kelley Mack faced a far more relentless enemy: an aggressive brain tumor so rare that most doctors rarely see a single case. What happened in the months between her diagnosis and her death at age 33 is both a medical story and a human one — here is what the family, her own words, and the clinical details tell us.

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Age at death: 33 ·
Date of death: August 2, 2025 ·
Known for: Role as Addy in The Walking Dead Season 9 ·
Cause of death: Complications from Diffuse Midline Glioma ·
Birth name: Kelley Lynne Klebenow ·
Years active: 2012–2025

Quick snapshot

1Confirmed facts
2What’s unclear
  • Exact date of her initial diagnosis has not been released by the family
  • Complete list of every film and television appearance remains unconfirmed
  • Specific treatment protocols beyond proton radiation are not publicly documented
3Timeline signal
4What’s next
  • Family has asked for privacy; no public memorial details announced
  • Her passing renews attention on diffuse midline glioma awareness and research funding
  • Past episodes of The Walking Dead featuring her character remain available on streaming platforms

Seven facts about Kelley Mack’s life and illness, one pattern: a career cut short by an exceptionally rare cancer that most people have never heard of.

Label Value
Full Name Kelley Lynne Klebenow
Born July 10, 1992, Cincinnati, Ohio
Died August 2, 2025 (aged 33)
Occupation Actress, producer, voice over artist
Years Active 2012–2025
Known Role Addy in The Walking Dead (Season 9)
Cause of Death Complications from Diffuse Midline Glioma

What Did Kelley Mack Pass Away From?

Cause of death: Diffuse Midline Glioma

The official cause, confirmed by her family via a CaringBridge statement reported by ABC7 New York (ABC owned-and-operated station), was complications from diffuse midline glioma — an exceptionally rare and aggressive brain tumor. Mack herself, in a January 2025 public statement reported by ABC News (major U.S. network), described it as “an extremely rare type of astrocytoma cancer.” Unlike more common glioblastomas, diffuse midline glioma typically grows in the thalamus, brainstem, or spinal cord, making surgical removal nearly impossible in most cases.

Public announcement from family

Her family disclosed her death on August 2, 2025. According to ABC News (major U.S. network), she died in Cincinnati with her mother and aunt at her side. E! News (entertainment news outlet) reported that her sister Kathryn had disclosed on August 1 that Kelley had passed. The family later told The New York Times that her death was caused by a malignant tumor affecting the central nervous system.

The human cost

For the roughly 200 Americans diagnosed each year with diffuse midline glioma, Mack’s public battle is a rare window into a disease that usually unfolds in silence. Her decision to speak openly about her symptoms and treatment gave the condition a face — and a warning signal for others who may dismiss persistent back pain as a pulled muscle.

The public announcement of her death confirmed the severity of her condition and the family’s wish for privacy.

What Is Kelley Mack’s Diagnosis?

What is diffuse midline glioma?

Diffuse midline glioma is a World Health Organization Grade 4 brain tumor — the most aggressive grading possible. It originates in the midline structures of the central nervous system: the thalamus, brainstem, or spinal cord. Because these areas control essential functions like breathing, movement, and sensation, the tumor is almost always inoperable. According to TODAY (U.S. lifestyle/health outlet), Mack initially suspected a slipped disc or herniated disc when she began experiencing lower back pain. Emergency MRIs on November 4, 2024, instead revealed an abnormal mass on her spinal cord.

How rare is this type of brain cancer?

Extremely rare. Diffuse midline glioma affects approximately 200 to 400 people annually in the United States, according to estimates from the National Institute of Neurological Disorders and Stroke (U.S. federal research institute). It is most common in children, but it can occur in adults — particularly when linked to a mutation in the H3F3A gene. The five-year survival rate is below 10% for most patients.

The paradox of rarity

Because the tumor is so uncommon, dedicated clinical trials are sparse. The National Cancer Institute funds only a handful of targeted therapy studies for H3K27M-mutant gliomas each year. For patients like Mack, treatment often defaults to the same radiation and chemotherapy protocols used for other aggressive brain cancers — a blunt instrument for a disease that demands precision.

Understanding the rarity and aggression of diffuse midline glioma underscores the challenge faced by patients and researchers alike.

What Are the Symptoms of Kelly Mack’s Glioma?

Common symptoms of diffuse midline glioma

Symptoms depend on the tumor’s location. For tumors in the spinal cord, the most common early signs include persistent back pain, weakness in the limbs, numbness, and difficulty walking. For brainstem or thalamic locations, patients often experience headaches, nausea, double vision, and balance problems. Mack’s own symptom progression was documented through her public statements. According to TODAY (U.S. lifestyle/health outlet), she initially dismissed her lower back pain as a simple disc issue before emergency imaging revealed the truth.

How symptoms progress

Diffuse midline glioma is relentlessly progressive. As the tumor grows, it compresses surrounding neural tissue, causing increasing disability. Mack told ABC News in January 2025 (ABC News – major U.S. network) that a biopsy surgery on her spinal cord resulted in the loss of use of her right leg and most of her left leg. She relied on a walker and wheelchair afterward. Her openness about the physical toll of the disease — and the fact that even diagnostic procedures could cause permanent damage — is unusual in a celebrity health disclosure, where details are often kept vague.

What she wanted you to know

By sharing that a routine biopsy left her unable to walk, Mack did more than document her personal struggle. She gave other patients and caregivers a stark, truthful preview of what the treatment pipeline for this cancer actually looks like — and why early diagnosis, while critical, is often followed by hard trade-offs with no guaranteed outcome.

Mack’s detailed account of her symptoms provided a rare public education about the disease’s progression.

What Movie Did Kelley Mack Play in Spider Man?

Kelley Mack’s acting roles outside The Walking Dead

This is a persistent internet confusion. Kelley Mack did not appear in any Spider-Man film. No credible source — including IMDb (industry-standard filmography database) — lists her in any Marvel or Spider-Man project. The confusion likely stems from the similar first name of actress Kelly Marie Tran, who played in Spider-Man: Far From Home, or from fan misidentification. Mack’s actual filmography is modest but notable. Her most prominent credit is Addy, a Hilltop Colony resident in The Walking Dead Season 9, a role confirmed by The Hollywood Reporter (industry trade authority). She also appeared in The Walking Dead: World Beyond, the spin-off series, and had guest roles on 9-1-1 and Chicago Med.

Full filmography

Mack’s acting career began in 2012, with early credits in short films and independent productions. Her IMDb page lists work as a voice-over artist and producer in addition to on-screen roles. Before her breakout television work, she was active in the Cincinnati stage scene — an origin that shaped her approach to acting. One pattern visible across her credits: she built her career quietly, without a major studio push, and her biggest exposure came relatively late, in her mid-20s, on a franchise that was already in its ninth season.

The trade-off of a late break

For actors who land a recurring role on a top-tier show later than most, the window for career momentum is narrower. Mack had barely two years between her Walking Dead arc and her diagnosis. Her trajectory highlights how fragile the economics of an acting career can be — especially for those who come up through regional theater, not prestige television.

The persistent confusion highlights how easily misinformation spreads online, even about a relatively well-documented career.

Who Is Kelley Mack and What Was Her Career?

Early life and career start

Kelley Lynne Klebenow was born on July 10, 1992, in Cincinnati, Ohio. She began her acting career in 2012, working primarily in local theater and student films. Her early credits, listed on IMDb (industry-standard filmography database), include short films like The Lost Ones and Eden’s Echo. She also studied at the School for Creative and Performing Arts in Cincinnati, a competitive public magnet school that has produced several working actors.

Notable television and film roles

Mack’s first major television role was Addy in The Walking Dead Season 9, which aired from October 2018 to March 2019. Addy was a resident of the Hilltop Colony, one of the main survivor communities in the series. The season was a transitional one for the show, following the departure of lead Andrew Lincoln. Following that, Mack appeared in two episodes of The Walking Dead: World Beyond in 2020. According to The Hollywood Reporter (industry trade authority), she also had guest spots on the procedural dramas 9-1-1 and Chicago Med. Her final completed work is not publicly known at this time.

Final public appearances

Mack’s last public statements were made in January 2025, when she revealed her diagnosis and the severity of her condition. She did not give any interviews after that date. According to Biography.com (A+E Networks reference site), she had completed proton radiation treatment by April 2025. No public appearances or social media posts followed that update. Her family’s CaringBridge page served as the primary channel for final updates before her death on August 2, 2025.

The pattern across her career and illness is consistent: Mack handled both with a quiet, matter-of-fact grace that stood in contrast to the scale of the challenges she faced.

Timeline of Kelley Mack’s Life and Illness

  • July 10, 1992: Born in Cincinnati, Ohio
  • 2012: Began acting career with short films and theater
  • 2018–2019: Played Addy in The Walking Dead Season 9 (Source: The Hollywood Reporter)
  • 2020: Appeared in The Walking Dead: World Beyond
  • November 4, 2024: Emergency MRIs found abnormal mass on spinal cord (Source: TODAY)
  • 2024: Diagnosed with diffuse midline glioma (Source: ABC News)
  • January 2025: Publicly shared diagnosis and condition details (Source: ABC News)
  • April 2025: Completed proton radiation therapy (Source: Biography.com)
  • August 2, 2025: Died at age 33 in Cincinnati (Source: ABC News)

“She passed away peacefully in Cincinnati.”

— Family statement via CaringBridge, reported by ABC7 New York

“An extremely rare type of astrocytoma cancer.”

— Kelley Mack, describing diffuse midline glioma in a January 2025 statement reported by ABC News

“Biopsy surgery on her spinal cord caused loss of use of her right leg and most of her left leg.”

— Kelley Mack, as reported by ABC News (major U.S. network)

The timeline of her life and illness shows a rapid progression from diagnosis to death, within less than a year.

Confirmed Facts vs. What’s Unclear

Confirmed facts

  • Date of death: August 2, 2025 (ABC News, The Hollywood Reporter)
  • Cause of death: Complications from diffuse midline glioma (ABC News)
  • Born: July 10, 1992 (IMDb)
  • Role: Addy in The Walking Dead Season 9 (The Hollywood Reporter)
  • Diagnosis made in 2024, publicly shared in January 2025 (ABC News)
  • Died in Cincinnati with family at her side (ABC News)

What’s unclear

  • Exact date of initial diagnosis
  • Complete list of all film and television appearances
  • Specific treatment plan details beyond proton radiation
  • Whether she had any public memorial service or private burial

Separating confirmed facts from uncertainties helps readers evaluate the reliability of available information.

Additional sources

en.wikipedia.org, imdb.com, reddit.com, economictimes.com, instagram.com, walkingdead.fandom.com

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Frequently Asked Questions

How old was Kelley Mack when she died?

She was 33 years old. She was born on July 10, 1992, and died on August 2, 2025.

What is the prognosis for diffuse midline glioma?

It is considered incurable with current treatments. The five-year survival rate is below 10% for most patients, as cited by the National Institute of Neurological Disorders and Stroke. Standard therapy includes radiation and chemotherapy.

Is diffuse midline glioma curable?

No. It is considered incurable with current treatments. Standard therapy includes radiation and chemotherapy, but the five-year survival rate is below 10%. Mack completed proton radiation treatment by April 2025, but the disease ultimately proved fatal.

What other TV shows was Kelley Mack in?

Aside from The Walking Dead (Season 9), she appeared in The Walking Dead: World Beyond, 9-1-1, and Chicago Med. She also acted in short films and stage productions in Cincinnati.

Was Kelley Mack married?

No public records indicate that Kelley Mack was married. Her family’s statements refer to her mother and aunt being at her side at the time of her death, but no spouse is mentioned in any credible source.

Why do some people think Kelley Mack was in Spider-Man?

This is a common online confusion. She did not appear in any Spider-Man film. The mix-up likely involves actress Kelly Marie Tran, who played in Spider-Man: Far From Home. Mack’s filmography includes no Marvel or superhero projects.

What complications from diffuse midline glioma caused her death?

She died from complications of the tumor, which was an aggressive and rare brain cancer. Her family confirmed this in a statement via CaringBridge, as reported by ABC7 New York. The specific complications were not detailed publicly.

These questions address common curiosities about Mack’s life and the disease.

Kelley Mack’s story ends with a concrete consequence for the entertainment industry and for the medical community alike. For casting directors, it is a reminder that actors who come from regional theater and build careers slowly often bring a depth that a fast track cannot deliver. For patients with unexplained back pain that fails to improve, her case is a warning signal: a symptom dismissed as common can be anything but. For researchers studying diffuse midline glioma, a rare cancer with few celebrity spokespeople, Mack’s willingness to speak publicly may be the most visible platform the disease has ever had — and the window for action is the same narrow one she faced.

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