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Kelley Mack death cause: What is the rare brain cancer that claimed her life?

Actress and voiceover artist Kelley Mack, best known for her role as Addy on The Walking Dead, has died at 33 after a private battle with diffuse midline glioma, a rare and aggressive brain cancer.
August 06, 2025 / 11:14 IST
Actress and voiceover artist Kelley Mack — best known for her role of Addy in The Walking Dead — has died at the young age of 33

Actress and voiceover artist Kelley Mack — best known for her role of Addy in The Walking Dead — has died at the young age of 33. On August 5, her family announced her heartbreaking demise via her official account on Instagram.

The statement continued: "We are heartbroken to announce that our sweet Kelley has passed away. "A bright, fiery light has crossed over; somewhere we all must eventually cross over to "

She died on Saturday evening surrounded by her mother, Kristen, and her aunt Karen, a post said. Speaking about Kelley, her loved ones said, "In the form of all the butterflies she has already sent us all… hundreds of them," in a heartfelt reference to her spirit.

While the family never stated the specific illness publicly, the actress had written about fighting diffuse midline glioma (DMG) — a rare and ultra-aggressive brain cancer.

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What Is Diffuse Midline Glioma?

Diffuse Midline Glioma is a highly malignant brain tumour that occurs most often in children and young adults. It occurs in central structures of the brain, such as the thalamus, brainstem or spinal cord, that maintain basic life functions, says Dr. Radhika Sharma, Senior Neuro-Oncologist in New Delhi.

It is one of the most complex brain cancers, and surgical removal is not possible, and the treatment is challenging.

Before a diagnosis of Diffuse Midline Glioma is made, patients may exhibit some signs of this disease.

“Because DMG impacts critical midline structures in the brain, symptoms are based on where the tumor is located,” says Sharma. Most of them move rapidly, but very early manifestations can be difficult to identify:

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  • Chronic headaches — typically occurring in the morning and not treated as normal
  • Problems with balance and coordination — Trouble walking, falling down a lot, or being clumsy.
  • Facial Weakness or Numbness – One side of the face may droop or feel numb.
  • Eye movement abnormalities or double vision — Cranial nerve involvement
  • Slurred Speech or Difficulty Swallowing — Indicating Compression of The Brainstem
  • Weakness and Personality Change — An emotional way of a dormant or psychotic individual or when there is cognitive confusion.

Diagnosis and Treatment

The first step in diagnosing DMG is an MRI scan, which shows where the tumour is and how it is developing. A biopsy may be done in order to verify the genetic mutation in some cases.

As is the case with DMG, however, there are few treatment options available. Surgery is rare since the tumour invades delicate brain areas. Standard treatment may include:

Radiation Therapy – This offers short-term relief and inhibits cancerous growth.

Clinical Trials— New targeted therapies in clinical trials that target the H3K27M mutation.

Corticosteroids and Supportive care — Help relieve symptoms and improve the quality of life

Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for a specific health diagnosis.

Nivedita is a Delhi-based journalist who writes on health, fashion, lifestyle and entertainment. Views expressed are personal.
first published: Aug 6, 2025 10:30 am

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