• As varied as in children, more complicated to diagnosis because adults have acquired other diseases through the years. Mitochondrial diseases tend not to present as catastrophic events.
• Childhood onset mitochondrial diseases that become increasingly obvious as the person ages
• Muscle: new muscle weakness, cramping, fatigue
• Brain: migraine, stroke or stroke-like events, dementia, MS-like presentation
• Endocrine: diabetes (~5% of DM may be due to the mtDNA 3243 mutation)
• Cardiac: early cardiomyopathy, cardiac conduction defects (association of LHON with WPW, etc)
• Systemic: CFS-like illness (Chronic Fatigue Syndrome - like illness)

Many experts refer to Mitochondrial Disease as the "Notorious Masquerader" because it wears the mask of many different illnesses.

Additional Adult Brief Differential Diagnoses to Consider

• Primary endocrine disease
• Vitamin deficiency: B12
• Homocystinuria and associated disorders
• Primary muscle disease: polymyositis, dystrophin associated glycoprotein muscular dystrophies
• Chronic fatigue syndrome
• Autoimmune disorders
• Glycogen storage disorders
• Depression and related psychosomatic disorders
• Other neurodegenerative disorders (MS, ALS, HD, combined systems degeneration)

Mitochondrial disease is diagnosed by:

• Evaluating the patient's family history
• Performing a complete physical examination
• Performing a neurological examination
• Performing a metabolic examination that includes blood, urine, and optional cerebral spinal fluid tests
• Performing other tests, depending on the patient's specific condition and needs. These tests might include:
  • Magnetic resonance imaging (MRI) or scan (MRS) if neurological symptoms are present
  • Retinal exam or electroretinogram if vision symptoms are present
  • Electrocardiogram (EKG) or echocardiogram if heart disease symptoms are present
  • Audiogram or BAEP if hearing symptoms are present
  • Blood test to detect thyroid dysfunction if thyroid problems are present
  • Blood test to perform genetic DNA testing