The Walking Dead star Kelley Mack dies aged 33 from rare brain cancer as symptoms explained

The Walking Dead star Kelley Mack has died at the age of 33.

The actress, who played Addy in season nine of the AMC drama, passed away 'peacefully' on Saturday, August 2, with 'her loving mother Kristen and steadfast aunt Karen present'.

Mack had been diagnosed with glioma of the central nervous system - a 'rare' form of cancerous tumor. She went public with her diagnosis last year.

Her family shared the sad news of her death via Instagram, writing, in part: "It is with indelible sadness that we are announcing the passing of our dear Kelley. Such a bright, fervent light has transitioned to the beyond, where we all eventually must go.

"Kelley passed peacefully on Saturday evening with her loving mother Kristen and steadfast aunt Karen present. Kelley has already come to many of her loved ones in the form of various butterflies. She will be missed by so many to depths that words cannot express."

Tributes flooded in for the actress, including from The Walking Dead's Alanna Masterson, who played Tara Chambler.

She wrote: "What an incredible human. So proud to have fought alongside her in our final episode together."

Mack - full name Kelley Lynne Klebenow - racked up an impressive 35 acting credits and five producer credits across her career, including Penelope Jacobs in Chicago Med and Fox’s 9-1-1. She had most recently starred in the drama-comedy movie Universal, alongside The Inbetweeners star Joe Thomas.

Back in January, Mack revealed she'd began her first of 24 rounds of proton therapy. By March, she'd finished the treatment and underwent what appeared to be gruelling physical therapy, reporting that 'things are getting better.'

Mack is survived by her mother and father, Kristen and Lindsay Klebenow, sister Kathryn, brother Parker, grandmother and grandfather Lois and Larry Klebenow and boyfriend, Logan Lanier.

Symptoms of glioma explained

Mack had been diagnosed with a 'rare subtype' of glial tumor called a diffuse midline glioma. These affect the primary central nervous system and begin in the brain or spinal cord, according to the National Cancer Institute (NCI).

Mack first noticed 'persistent lower back pain' in October 2024, with escalated to the point of her being rushed to hospital the night before Thanksgiving.

An MRI scan revealed an 'abnormal mass' on her spinal cord.

The NCI explains that diffuse midline gliomas are all grade 4 - meaning they're 'cancerous and fast-growing.'

Symptoms usually depend on where in the body the tumor is growing. They can include double vision, problems swallowing, weakness in one or both sides of the body and loss of balance.

People with a tumor growing in the spine might experience progressive weakness, numbness and problems with bowel and bladder control.

Around 3,940 people are living with diffuse midline glioma in the US, the NCI says.

If you’ve been affected by any of these issues and want to speak to someone in confidence, contact the American Cancer Society on 1-800-227-2345 or via their live chat feature, available 24/7 every day of the year.