Mitochondrial Disorders

Question 1

Whate is heteroplasmy?

Answer 1

Refers to the concept that not all mitochondria in the same cell may have the same genetic make up.

Question 2

Kearns-Sayre Syndrome

Answer 2

Commonly caused by a somatic mutation

What is the mutation?

• Single large deletion of mtDNA
• Most common deletion removes twelve genes

Clinical signs:

•Triad
–Pigmentary Retinopathy
–Progressive External Ophthalmoplegia
–Onset before age 20y
•Cardiac conduction defects
•Ataxia
•Deafness
•Kidney problems

Question 3

MELAS

Answer 3

Gene MT-TL1 (80%)

Clinical Signs:

• Starts between age 2 & 10 y
• Muscle weakness
• Seizures
• Repetitive stroke-like episodes
• Elevated **lactate/ lactic acidosis

Question 4

MERRF

Answer 4

Gene mutated: MT-TK

Clinical signs:

• Muscle weakness
• Seizures
• Ataxia
• Dementia
• *-Ragged-red fibers**

Question 5

Leber Hereditary Optic Neuropathy

Answer 5

• Bilateral subacute vision failure
• Occurs during young adulthood