COMMENTARY

My Patient May Have a Mitochondrial Disease: What Should I Do?

Marni J. Falk, MD

Disclosures

August 17, 2018

Editorial Collaboration

Medscape &

Hello. My name is Dr Marni Falk. I am a geneticist here at the Children's Hospital of Philadelphia.

If you suspect that a patient that you follow has a mitochondrial disease, what should you do? Ideally, you would seek the counsel of somebody who has expertise in mitochondrial medicine, typically including a genetics expert; a metabolic disease doctor; or often, a neurologist.

There are things that you can do as a primary clinician, however, right up front.[1] This includes checking basic laboratory studies, such as chemistry panels, to make sure there is no liver or kidney dysfunction. Also check an anion gap, and a lactate or pyruvate level to determine whether there is an increased acid load in the blood, as would be seen in a metabolic acidosis with an anion gap.

There are also other metabolic screening studies that can be useful in some instances, such as amino acid studies, organic acid studies, and acylcarnitine profiles. However, there is no one specific marker that can confirm or refute that somebody has a mitochondrial disease.

More often, genetic testing is more useful up front, including mitochondrial DNA sequencing in the affected tissue or, increasingly, in the blood, depending on the methodology used. Large panels of nuclear genes or, in many cases, exome and, in the future, whole-genome sequencing may identify the precise cause of any individual patient's medical problems.

If you confirm that your patient does indeed have a mitochondrial disease, what should you do? Certainly, you should get them seen by a mitochondrial medicine center, of which there are many around the country. There are screening studies that should be done according to standard of care guidelines published in 2017.[2]

These include screening evaluations of the heart, including an echocardiogram and an EKG; audiology evaluation for sensorineural hearing loss, which is often high-frequency and progressive, and an ophthalmologic exam, including a dilated exam, to look for retinal or optic nerve dysfunction that is common in this group of disorders. If there is neurologic dysfunction, the patient should be seen by a neurologist and a brain MRI should be considered. Brain MRS or spectroscopy study are often useful, if available, to look for such chemicals as lactic acid in different aspects of the brain.

A very thorough review of systems should be obtained. On the basis of the symptoms that are present, clinical care should be sought, including looking for other metabolic conditions, such as dyslipidemia, diabetes, or hormonal dysfunction, such as adrenal insufficiency or thyroid dysfunction that occurs not uncommonly.

It is important to note that the onset of mitochondrial disease can be at any point in the lifespan. Someone can have a healthy childhood and present with mitochondrial disease as an adult. It is also important to recognize that the features of mitochondrial disease in any one given patient can change over time. It is important to stay vigilant and, if you have somebody whose function is abnormal even in the absence of an identifiable biomarker or structural problem, think about the possibility that energy failure could be underlying their condition, which [could be indicative of] a mitochondrial disease.

Strong consideration should also be given to starting a mitochondrial medicine supplement regimen. There are multiple resources and information available through the Mitochondrial Medicine Society and the United Mitochondrial Disease Foundation.

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