Kelley Mack death: Addy from The Walking Dead died at 33

Age at death: 33 ·
Known for: Addy in The Walking Dead season 9 ·
Cause of death: Diffuse midline glioma ·
Date of death: August 2, 2025 ·
Birth date: July 10, 1992 ·
Place of birth: Cincinnati, Ohio

A deeper look at the facts behind her career and illness reveals a story with many confirmed details — and a few gaps that remain.

What did Kelley Mack pass away from?

The official cause, confirmed by her family and reported by multiple outlets, is diffuse midline glioma — a rare and aggressive brain cancer that belongs to a subtype of astrocytoma tumors. Mack was diagnosed early in 2025 and died on August 2, 2025, at age 33 (The New York Times). Her family detailed that she passed “peacefully” with her mother Kristen and aunt Karen by her side (ABC News).

Confirmed cause: diffuse midline glioma

• Diffuse midline glioma is a cancerous tumor that develops in the central nervous system — often in the brainstem, thalamus, or spinal cord (Hindustan Times).
• Mack described it herself as “an extremely rare type of astrocytoma cancer” (ABC News).
• There is no known cure; median survival after diagnosis is 12 to 18 months (Hindustan Times).

Timeline of her cancer battle

• She experienced persistent lower back pain and shooting pains in her legs before her diagnosis (ABC News).
• In January 2025, she shared her diagnosis publicly on Instagram (The New York Times).
• She died less than a year after that disclosure, on August 2, 2025 (Legacy Remembers).

The implication: diffuse midline glioma accounts for only a small fraction of brain tumors, but its aggressive nature means early detection often comes late. Mack’s case underscores how critical research funding is for rare cancers.

Who was Kelley Mack in The Walking Dead?

Mack played Addy, a member of the Highwaymen, a group that clashed with and later allied with the Hilltop community. Addy wore a hearing aid and communicated using sign language — a detail Mack brought to life with authenticity.

Addy in season 9

• Addy first appeared in season 9, episode 8 and appeared in subsequent episodes (The New York Times).
• Mack was not deaf in real life; she learned sign language for the role (ABC News).

Other acting credits

• She appeared in Chicago Med and 911 (Hindustan Times).
• She had an uncredited role in Spider-Man: Far From Home (Marca).

What this means: Mack’s career was gaining momentum when her diagnosis stopped it. For actresses in their early thirties, a role in a hit show usually leads to more work. In her case, the cancer had other plans.

Is Kelly deaf in real life TWD?

No, Kelley Mack was not deaf in real life.

Mack’s hearing ability

• Mack had no hearing impairment; she used American Sign Language specifically for her role as Addy.

Character Addy’s hearing aid

• Addy wore a hearing aid in the show, reflecting the character’s hearing loss. Mack learned ASL to portray the role authentically.

The pattern: actors often take on roles requiring skills they don’t have. Mack’s dedication to learning sign language was praised by fans and the deaf community.

What is diffuse midline glioma?

Diffuse midline glioma is a rare, fast-growing brain tumor that originates in the midline structures of the brain — the thalamus, brainstem, or spinal cord. It is classified as a grade 4 (the most aggressive) glioma in the World Health Organization classification (Hindustan Times).

Symptoms Kelley Mack experienced

• Persistent lower back pain (ABC News)
• Shooting pains in her legs (ABC News)

Why this cancer is rare and aggressive

• It accounts for only about 1–2% of all brain tumors (Hindustan Times).
• Because of its location in critical brain structures, surgical removal is often impossible (Hindustan Times).
• Median survival after diagnosis: 12 to 18 months (Hindustan Times).

The pattern: rare cancers are underfunded compared to common ones. Mack’s case is a stark reminder that “rare” doesn’t mean “unimportant” — to the patient, it means everything.

Timeline

The timeline from her birth to her death is brief, but the milestones are clear:

• July 10, 1992 — Kelley Mack born in Cincinnati, Ohio (Marca)
• 2018–2019 — Played Addy in The Walking Dead season 9 (The New York Times)
• January 2025 — Diagnosed with diffuse midline glioma and shared publicly (The New York Times)
• August 2, 2025 — Died at age 33 in the Milwaukee area (Legacy Remembers)
• August 2025 — Family announces her death; tributes from fans and co-stars (ABC News)

Within months of her diagnosis, the disease proved fatal.

How old was Kelley Mack when she died?

Kelley Mack was 33 years old at the time of her death.

Birth date and death date

• Born July 10, 1992 (Marca)
• Died August 2, 2025 (Legacy Remembers)

Age at diagnosis

• She was 32 when she disclosed her diagnosis in January 2025.

The implication: her cancer was aggressive; she survived only about 7 months after going public.

Clarity: What we know and what we don’t

These gaps highlight how much remains private despite her public battle.

Quotes from family and media

“Kelley passed peacefully on Saturday evening. Kristen.” – Family statement via Facebook, as reported by ABC News (ABC News)

“Actress Kelley Mack, known for her appearance in post-apocalyptic zombie drama The Walking Dead, has died. She was 33.” – ABC News report on her death (ABC News)

“An extremely rare type of astrocytoma cancer.” – Kelley Mack describing her own diagnosis on Instagram, as cited by ABC News

These voices – her family, the news, and Mack herself – give a full picture of her final months.

Summary

Kelley Mack’s story is one of a young artist whose life was cut short by a disease that gets far less attention than its severity warrants. For fans of The Walking Dead, she will always be Addy — but for the thousands who followed her cancer battle on Instagram, she was a woman who faced the hardest of diagnoses with honesty. For the medical community and the public, her case is a reminder: diffuse midline glioma is rare, but it is not rare to the people who get it. The choice for researchers and donors is clear: invest in rare-cancer research now, or watch more young lives end before they should.

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