The Walking Dead actor Kelley Mack dies at 33 as rare cancer illness explained

The Walking Dead actor Kelley Mack has died at the age of 33 after being diagnosed with a rare form of cancer.

Mack was best known for her role as Adeline in season nine of the AMC zombie TV show. Adeline was a survivor of the apocalypse on the show as part of the Hilltop community and appeared in five episodes.

Aside from The Walking Dead, Mack also provided additional voices on Spider-Man: Into the Spider-Verse and an episode of 9-1-1.

On 5 August, the news of her death was announced by her family, who'd posted to Instagram and their CaringBridge page saying: “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. She will be missed by so many to depths that words cannot express."

Kelley Mack was best known for her role in The Walking Dead (AMC)

What is a glioma?

On 3 January, Kelley shared on her Instagram that she'd been diagnosed with diffuse midline glioma (DMG), a rare form of cancer.

DMG is a glioma of the central nervous system, usually of the brain or spine. It is a cancer which is estimated to affect just 2-300 people annually in the US, with gliomas generally making up roughly 25 per cent of the 80,000 brain tumours diagnosed every year.

A glioma is any tumour that originates from glial cells found in the brain, and some forms are more treatable than others, with the location of the tumour being a huge factor when it comes to treatment.

In her post, she said she'd been suffering from 'persistent back pain' since September, adding: "A few weeks later, I had neuropathic itching in my right quad. And then, the shooting pains in my legs and back began, which resulted in me having to sleep in a recliner for a month because laying down was too painful.

"On Thanksgiving Eve, I had emergency MRIs done at the hospital, which revealed an abnormal mass in my spinal cord."

She went on to say that 'due to a biopsy surgery on my spinal cord', she'd lost 'the use of my right leg and most of my left leg', and relied on a walker and wheelchair to move around.

What are the signs of a glioma?

Kelley recently completed proton radiation treatment in April (Instagram / ItsKelleyMack)

Though DMGs specifically are more common amongst children (under 12) and elderly adults (over 65), people of any age can develop gliomas.

According to DMG.org, the following symptoms are clinical signs of a Diffuse Midline Glioma:

• odd eye movements
• slurred speech
• difficulty swallowing
• trouble maintaining balance
• drooping of one part of the face
• persistent headaches, nausea, and vomiting

The organisation adds that DMG tumours can 'press on and interfere with the function of these nerves, leading to weakness in an arm and/or a leg', as well as causing 'increased pressure on the skull'.

An MRI is the best way to determine if someone is suffering from a DMG; however, in rare cases, this may only show up on a biopsy.

Ana Carolina Goncalves, superintendent pharmacist at Pharmica, told The Independent that depending on where the tumour is, some can be treated with surgery, while others might require treatments such as 'chemotherapy, radiotherapy and proton beam radiotherapy'.

According to Kelley's friend, Chelsea, the actor had 'completed proton radiation' in April, as she wrote on CaringBridge: "She is regaining walking abilities."

If you’ve been affected by any of these issues and want to speak to someone in confidence, contact Macmillan’s Cancer Support Line on 0808 808 00 00, 8am–8pm seven days a week.