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Kelley Mack’s Fight With Rare Cancer: What’s Diffuse Midline Glioma?

woman having a severe headache

Health & Wellness

Actress Kelley Mack died at age 33, following a battle with diffuse midline glioma (DMG), a rare and aggressive tumor that affects the central nervous system.

What’s Diffuse Midline Glioma?

DMG is a fast-growing tumor that forms in the brain or spinal cord. It begins in glial cells, or supportive cells that help the nervous system function properly.

DMG is difficult to treat because it spreads through the tissue, making surgical removal nearly impossible. Most cases are linked to a specific genetic mutation which causes rapid tumor growth.

Because of its location and invasive nature, treatment options are limited.

Kelley Mack’s Symptoms and Diagnosis

In January, Mack shared a health update on Instagram, describing the early symptoms that led to her diagnosis.

Her first symptoms appeared in September 2024. She experienced persistent lower back pain and a strange itching sensation in her right thigh that couldn’t be relieved by scratching. This was later identified as neuropathicitching, caused by nerve irritation or damage.

Her condition worsened over time. She developed shooting pain in both legs and became so uncomfortable that she had to sleep sitting upright because lying down caused intense pain. An emergency MRI revealed an abnormal mass along her spinal cord and led to the diagnosis of diffuse midline glioma.

Warning Signs You Shouldn’t Ignore

“Despite surgery, radiation, and chemotherapy, brain tumor gliomas aren’t always curable,” said Robert M. Starke, MD, co-director of endovascular neurosurgery at Jackson Memorial Hospital, and a UHealth – University of Miami Health System neurosurgeon and neuroradiologist. “Symptoms to look out for include progressive weakness or numbness on one side of the body, shaking movements consistent with seizures, progressive headaches that don’t respond to over-the-counter medications, confusion, behavioral alterations, or other neurological alterations.”

Ongoing or worsening symptoms should be checked by a doctor, especially if they include:

  • Burning, tingling, or itching that doesn’t improve
  • Weakness or difficulty walking
  • Pain that worsens when lying down
  • Numbness or unusual sensations in the limbs
  • Unexplained decline in strength or mobility, especially in young adults

When to See a Specialist

If symptoms persist for more than a few weeks or become severe, consider seeing a neurologist. They can:

  • Perform a neurological exam
  • Order imaging tests, such as a MRI or CT scan
  • Help distinguish between common issues and serious neurological problems

If a mass is found, a neurosurgeon may be consulted to:

  • Evaluate surgical options
  • Recommend a biopsy or other diagnostic procedures
  • Treatment, including radiation or advanced therapies

Treatment and Outlook

DMG is especially hard to treat. Surgery is rarely an option, and standard chemotherapy and radiation often have limited effect. Some patients undergo high-dose radiation, proton therapy, or enroll in clinical trials.

Mack openly documented her treatment and life changes. Her story helped raise awareness of a disease that’s still little-known outside the medical community.

Though outcomes for DMG remain difficult, early diagnosis and access to specialty care may help patients explore treatment options and manage symptoms more effectively.

For more information on neurosurgery options at Jackson Health System, visit our website at https://jacksonhealth.org/services/neurosurgery/.