Mitochondrial Diseases

What are the features seen in mitochondrial diseases?

One hallmark of mito is that it is a multiorgan disease.

Most cells in the body have mitochondria. The areas of the body that rely on mitochondria the most are the brain, spinal cord, heart, muscles, kidneys, stomach, intestines and endocrine glands (e.g., thyroid and pancreas). This is because these tissues have a large percentage of mitochondria.

With mito, these organs may not function properly, leading to the following symptoms:

• Muscle weakness or ‘heaviness’
• Vision or hearing problems
• Liver or kidney disease
• Diabetes mellitus
• Gastrointestinal problems
• Short stature and poor weight gain
• Brain problems such as seizures and stroke-like episodes

People with mito can develop fatigue very suddenly. They may be unable to tolerate mild exercise. They may also take longer than usual to recover from a minor infection like a cold.

Types of mitochondrial diseases

Here are some of the more common mitochondrial syndromes:

1. Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS)
   MELAS usually starts in childhood to early adulthood. The hallmark of this syndrome is the ‘MELAS attack’: stroke-like episodes with seizures.
   
   Other clinical features include exercise intolerance, short stature, migraine-type headaches, inability to move the eyes, hearing loss, diabetes, digestive problems, heart problems, kidney disease and muscle weakness.

2. Chronic progressive external ophthalmoplegia (CPEO)
   CPEO is characterised by weakness of the eye muscles which may cause droopy eyelids and reduced ability to move the eyes. This often occurs in conjunction with other mitochondrial syndromes.

3. Kearns-Sayre syndrome (KSS)
   KSS usually starts before age 20. Common symptoms are a gradual inability to move the eyes (CPEO), difficulty seeing in the dark, heart problems and uncoordinated limb movements. Other symptoms may include hearing problems, kidney disease, diabetes or short stature.

4. Leigh syndrome: subacute necrotising encephalomyopathy
   Leigh syndrome usually starts in infancy and progression can be fast or slow.
   
   Disease characteristics include vomiting, uncoordinated limb movements, muscle weakness, muscle floppiness or spasticity, seizures, feeding and speech difficulties, hearing loss, abnormal eye movements, visual loss and motor and intellectual regression.