Understanding SANDO Syndrome

Finding a diagnosis for SANDO syndrome—an acronym for Sensory Ataxic Neuropathy, Dysarthria, and Ophthalmoparesis—is often a long and complex process ^[1][2]. Because this condition is rare and its symptoms overlap with many more common neurological disorders, it is not unusual for patients to spend years visiting different specialists before a genetic test provides the answer ^[2][3]. This page explains the core features of the syndrome, the biological cause rooted in your genes, and the common challenges of reaching a diagnosis.

The Three Components of SANDO

The name SANDO describes a specific combination of three symptoms, though not every patient will have all three components, and the severity varies. The “triad” of features includes:

• Sensory Ataxic Neuropathy: This is a type of nerve damage (neuropathy) that affects the nerves responsible for telling your brain where your limbs are in space. When these nerves are impaired, it leads to sensory ataxia—a loss of coordination and balance that often worsens in the dark or when you cannot see your feet ^[2][4].
• Dysarthria: This refers to difficulty speaking or slurred speech. In SANDO, this happens because the muscles used for speech do not receive the correct signals from the brain or nerves, making it harder to articulate words clearly ^[5][6].
• Ophthalmoparesis: This is the weakness or paralysis of the muscles that move the eyes. It often appears as ptosis (drooping eyelids) or a restricted range of eye movement ^[3][7]. Unlike many other conditions, this eye weakness usually affects both eyes and develops slowly over time ^[2].

The Biological Cause: POLG and Mitochondria

SANDO is caused by mutations in a gene called POLG ^[8][9]. This gene provides the instructions for making a protein called polymerase gamma, which is the principal tool your body has to replicate and repair the DNA inside your mitochondria ^[3].

Mitochondria are often described as the “power plants” of your cells because they produce the energy needed for your body to function. When the POLG gene is mutated, the “instruction manual” for building these power plants is broken ^[3]. Over time, your mitochondria may lose some of their own DNA or develop errors, leading to a shortage of energy in the tissues that need it most—specifically your nerves, brain, and eye muscles ^[3].

Because it is a genetic condition, SANDO is usually inherited in an autosomal recessive manner, meaning you likely inherited one mutated copy of the gene from each parent ^[9][10]. However, autosomal dominant variants of POLG disease also exist, which can complicate family testing. A referral to a genetic counselor is highly recommended to understand carrier status, reproductive options, and testing of relatives.

The Diagnostic Journey

If you were misdiagnosed with another condition before learning you have SANDO, your experience is common. Because SANDO is so rare, doctors may first test for more frequent conditions that look similar on initial exams:

• CIDP (Chronic Inflammatory Demyelinating Polyneuropathy): Doctors may mistake the nerve damage in SANDO for this immune-mediated condition, which also causes weakness and sensory loss ^[2][11].
• Miller Fisher Syndrome: This rare, immune-driven condition also features the “triad” of ataxia, eye weakness, and loss of reflexes, but it usually comes on very quickly after an infection, whereas SANDO is a lifelong, progressive condition ^[12][13].
• Other Mitochondrial Disorders: SANDO exists on a spectrum with other POLG-related disorders, such as Alpers-Huttenlocher syndrome or MEMSA, and it can be difficult to distinguish between them without detailed genetic sequencing ^[8][14].

Genetic testing is the definitive way to confirm SANDO. Current guidelines recommend comprehensive genetic testing of the POLG gene—often through exome or genome panels—rather than just checking for a few common mutations, as targeted screens can miss the specific variant responsible for your symptoms ^[15][16].

Understanding Progression and Uncertainty

Research has confirmed that SANDO is a progressive condition, but how it changes over time varies significantly between individuals ^[3][2].

• Age of Onset: SANDO can appear in early childhood or much later in life (though some cohorts noted an average onset around age 31) ^[3][7].
• Severity: Scientists are still working to understand why two people with the exact same POLG mutation can have very different symptoms ^[5][14]. Factors like your other genes, your environment, and the health of your mitochondrial DNA likely play a role in how the disease manifests ^[14]. Also, a variant of uncertain significance (VUS) on a genetic test does not automatically confirm the disease.
• Multisystem Involvement: Although the name focuses on nerves, speech, and eyes, some patients may also experience hearing loss, swallowing difficulties, or issues with other organs ^[6][2].

Because the condition is so variable, your care team will likely focus on supportive care—managing individual symptoms to improve your quality of life rather than following a single “one-size-fits-all” treatment plan ^[17][6].