How Ataxia-Telangiectasia Is Diagnosed

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Ataxia-telangiectasia (A-T) is a rare genetic disorder affecting the nervous system and blood vessels that often shows symptoms in infancy or early childhood. It is diagnosed in a clinical setting, where your doctor will consider a combination of factors.

Patient history, a thorough clinical evaluation, symptom identification, magnetic resonance imaging (MRI), and lab tests, including blood tests and karyotyping (a detailed evaluation of a person’s chromosomes), are typical in the diagnostic process. This article discusses how ataxia-telangiectasia is diagnosed and what to expect.

Shot of a doctor using a digital tablet to discuss a brain scan during a consultation in her office

Charday Penn / Getty Images

What Is Ataxia-Telangiectasia?

Ataxia-telangiectasia is a rare genetic disorder. Ataxia means the loss of control of body movements. Telangiectasia refers to spidery veins or dilated capillaries (blood vessels). These blood vessels show up as little purple or blue clusters on the skin or organs.

Self-Checks/At-Home Examination

Ataxia-telangiectasia has some very noticeable symptoms that typically develop early in life (between ages 1 and 3). These include abnormal movements, such as head swaying and trouble with walking and talking.

While a parenting adult may notice their child struggling and can take notes regarding symptoms, A-T cannot be confirmed in the home setting. If there is a family history of the condition, your pediatrician may provide you with a list of symptoms to watch for and report.

Certain neurological features may arise later, meaning a diagnosis of A-T should be carefully considered for any ataxic child with an otherwise elusive or difficult diagnosis.

Physical Examination

Noninvasive physical and neurological examinations may include slightly different tests depending on the individual being diagnosed. Assessments can differ to account for a person’s age, ability to participate, and level of consciousness.

The physical exam will pay particular attention to A-T impacted areas like:

  • Coordination or gait (walking)
  • Involuntary muscle movements like tics or tremors
  • Fluency of speech
  • Eye control

Your doctor will also thoroughly examine the common areas where symptoms of telangiectasia (dilated or noticeable blood vessels) are found in A-T. These include the bridge of the nose, the ears, and the whites of the eyes.

What Is Radiation Assay Testing?

People with A-T are known to have increased sensitivity to radiation therapy. Your doctor may decide to test a collected cell sample with radiation therapy to help confirm diagnosis. This is known as a radiation assay test. Depending on your location, results for this test can take around three months.

Labs and Tests

Blood work can help your doctors determine if you have the genetic markers associated with A-T.  Because A-T is so rare, these tests may be secondary to other blood tests that rule out more common diagnoses with similar symptoms.

If you have a family history of A-T, though, your doctor may order genetic blood testing earlier in the diagnostic process. Tests for A-T diagnosis include the following.


Karyotyping  is a procedure your doctor will use to evaluate the size, shape, number, and other characteristics of your chromosomes. Karyotyping takes place in a lab setting. Your doctor will collect some cells. After collection, the cells are tested using a staining method. People with A-T will demonstrate increased chromosomal abnormalities.

Ataxia-Telangiectasia Mutated (ATM) Gene 

There is a blood test that can check to see if you have this genetic mutation. When DNA (genetic material) is damaged, the ATM gene activates the p53 tumor suppressor protein. This keeps the damaged cells from dividing.

With a mutation to the ATM gene, cells with damaged DNA can continue to divide. This increases the risk of cancer. Your doctor will be able to determine the presence of the gene and its level of activity (known as protein kinase activity). ATM gene activity is found in 90% of cases of A-T.


Elevated levels of a blood protein called alpha-fetoprotein have been shown in approximately 85% of A-T cases. For children under 24 months old, this isn’t a good marker because levels can be elevated in unaffected children as well. A real difference cannot be detected until after age 2.

Immunoglobulin A (IgA) Deficiency

Immune system impairment is a characteristic part of living with A-T. A low level of IgA suggests some dysfunction of the immune system.


A complete blood count (CBC) and differential can test for lymphopenia—a lower count of certain white blood cells associated with fighting off infections. This type of blood testing is another way of checking immune system functioning.

Neurofilament Light Chain (NfL)

In a small study from 2021 published in the journal Cerebellum, researchers found significantly increased levels of NfL in patients with A-T compared to healthy subjects. This suggests NfL can be another blood biomarker for doctors to consider, but not to replace the other disease-specific genetic markers.


Brain Magnetic Resonating Imaging

A brain magnetic resonating imaging can check for signs of internal telangiectasia and other abnormalities. MRI machines do not use radiation. Instead, you’ll enter a tube-like structure, and a large magnet, radio frequencies, and a computer will work together to take pictures of the inside of your body.

Magnetic Resonance Angiography (MRA)

An MRA is a newer imaging technology that can be used in diagnosing A-T. MRA imaging looks specifically for abnormal blood vessels in the brain associated with telangiectasia.

Cancer Risk

People with A-T have about a 40% risk of developing cancer (leukemia and lymphoma). During and after the diagnostic process, people with A-T should be monitored closely for signs of cancer.

Differential Diagnosis 

A-T is a type of ataxia. Ataxia has many types that can be considered for a differential diagnosis, a process that differentiates between two or more conditions with similar presentations, or signs and symptoms. Some are hereditary, and others are not. Other disorders, including groups of movement disorders, also resemble A-T. 

Here’s a list of the common differential diagnoses for A-T:

  • Friedreich’s ataxia is inherited from both parents and impacts a person’s nerves and movement. Symptoms typically begin in late childhood and include trouble walking and slowed speech.
  • Marie’s ataxia (also called Pierre Marie’s disease or hereditary cerebellar ataxia) is characterized by unsteadiness walking. Symptoms start showing up in a person’s 30s or 40s. 
  • Charcot-Marie-Tooth (CMT) hereditary neuropathies is a group of disorders affecting sensory or motor nerves. They cause nerve damage that results in muscle weakness and atrophy, especially in the legs and hands. Atrophy means the size of the muscle is decreasing, or wasting away. 
  • Hereditary olivopontocerebellar atrophy (OPCA) is a group of rare disorders that eventually result in decreased abilities to walk, talk, and coordinate voluntary movements.


Ataxia-telangiectasia is often suspected due to symptoms in early childhood. A diagnostic workup includes physical and neurological examinations, genetic and blood tests, and magnetic resonance imaging. Other conditions that cause ataxia symptoms are considered before making the diagnosis.

A Word From Verywell

Diagnosing A-T can take some time. It is helpful to have a support system in place that can handle tasks like getting you to appointments and taking notes during follow-up visits for test results. In the meantime, know that getting a diagnosis sets you on the proper path to treatment and adjusting to living with A-T. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Organization for Rare Disorders NORD. Ataxia telangiectasia.  

  2. Rothblum-Oviatt C, Wright J, Lefton-Greif MA, McGrath-Morrow SA, Crawford TO, Lederman HM. Ataxia telangiectasia: a review. Orphanet J Rare Dis. 2016 Nov 25;11(1):159. doi:10.1186/s13023-016-0543-7

  3. American Society of Clinical Oncology. Ataxia-telangiectasia.

  4. Donath H, Woelke S, Schubert R, Kieslich M, Theis M, Auburger G, Duecker RP, Zielen S. Neurofilament light chain Is a biomarker of neurodegeneration in ataxia telangiectasia [published online ahead of print, 2021 Apr 24] [published correction appears in Cerebellum. 2021 Jun 2;:]. Cerebellum. 2021 Apr 24. doi:10.1007/s12311-021-01257-4

  5. Lin DDM, Barker PB, Lederman HM, Crawford TO. Cerebral abnormalities in adults with ataxia-telangiectasia. American Journal of Neuroradiology. 2014 Jan;35(1):119-123. 

  6. Johns Hopkins. Magnetic resonance imaging (MRI) of the brain and spine

By Michelle Pugle
Michelle Pugle, BA, MA, is an expert health writer with nearly a decade of contributing accurate and accessible health news and information to authority websites and print magazines. Her work focuses on lifestyle management, chronic illness, and mental health. Michelle is the author of Ana, Mia & Me: A Memoir From an Anorexic Teen Mind.