The Path to a Diagnosis

Because Mitchell Syndrome is a very new discovery, getting to the right diagnosis can often be a long and confusing journey. Many families find that their child is initially diagnosed with a more common condition before genetic testing reveals the true cause ^[1][2].

The Role of Genetic Testing

The diagnosis of Mitchell Syndrome is confirmed through genetic testing, typically a targeted ACOX1 panel, Whole Exome Sequencing (WES), or Whole Genome Sequencing (WGS) ^[1][3]. These tests scan your child’s DNA to look for specific changes.

Doctors often prefer trio sequencing, where they test the child and both biological parents at the same time ^[1]. This helps them determine if a genetic change is:

• De Novo: This means the mutation occurred spontaneously in the child and was not inherited from either parent ^[1][4]. Most reported cases of Mitchell Syndrome are de novo.
• Heterozygous: This means the mutation is found on only one of the two copies of the ACOX1 gene ^[4][5]. Because Mitchell Syndrome is a gain-of-function disorder, one mutated copy is enough to cause symptoms ^[6].

Why Misdiagnosis Can Happen

Because the symptoms of Mitchell Syndrome—like sudden coordination loss or nerve pain—can look like other diseases, it is sometimes mistaken for:

1. Autoimmune or Inflammatory Diseases: Because symptoms may appear in sudden “attacks” or episodes, doctors might first suspect Acute Disseminated Encephalomyelitis (ADEM) or Multiple Sclerosis (MS) ^[1][2]. Families may spend months on immune-suppressing treatments before the genetic cause is found ^[1].
2. Mitochondrial Disorders: The way Mitchell Syndrome may affect energy production and lead to elevated lactate levels in some patients can mimic mitochondrial diseases ^[1][7]. (Note: Elevated lactate is not always present).
3. Recessive ACOX1 Deficiency: As discussed on earlier pages, this is a different disease caused by having two broken copies of the gene. A child with Mitchell Syndrome will have the specific p.N237S mutation and usually has normal or only slightly elevated very-long-chain fatty acids (VLCFAs), whereas the recessive version typically shows high VLCFA levels ^[4][3].

It is important to remember that common, urgent diagnoses still need to be evaluated clinically. If your child presents with acute neurological symptoms, doctors must rule out infections and treatable autoimmune conditions, even if a genetic diagnosis is suspected.

Understanding Your Genetics Report

Genetics reports can be difficult to read. You should never try to self-interpret the results. Instead, review the report with a clinical geneticist or a genetic counselor. They will look for features reported in the original p.Asn237Ser cases, such as:

If the report shows two mutations (biallelic or homozygous) or a different protein change, the diagnosis may be recessive ACOX1 deficiency rather than Mitchell Syndrome ^[3][8]. Confident identification of the p.N237S variant is essential because it changes how doctors think about treatment, moving the focus toward reducing oxidative stress rather than just replacing a missing enzyme ^[6][4].

A Note on Interpretation: A laboratory report might not explicitly print the words “gain-of-function.” Furthermore, if a report lists a “Variant of Uncertain Significance” (VUS) or identifies two different variants, it requires expert interpretation. A VUS does not confirm a diagnosis, and having two variants might point toward recessive ACOX1 deficiency or simply be an incidental finding. Always rely on a genetics professional to explain what the findings mean for your child and to discuss family planning and recurrence risks.