Mitochondrial DNA Disorders

Question 1

Mitochondrial encephalopathy lactic acidosis and stroke (MELAS)

Answer 1

Heteroplasmic pattern

-caused by mutation in tRNA gene of mito DNA

Question 2

Pearson syndrome

Answer 2

Pancreatic insufficiency

• heteroplasmic
• due to large deletions in mito DNA
• get really sporadic caused due to somatic mutation

Question 3

Kare Sayre syndrome

Answer 3

Progressive myopathy, retinal pigmentation, and ataxia

• heteroplasmic
• due to large deletions in mito DNA

Question 4

Chronic progressive external ophthalmoplegia (CPEO)

Answer 4

Progressive atrophy of extra ocular muscles
-caused by either point mutation on a tRNA gene or deletion

Mode of transmission:

• maternal if point mutation
• sporadic if mutation is by deletion

Question 5

Alper’s disease

Answer 5

• mito DNA depletion syndrome characterized by dementia, seizures and liver disease
• autosomal recessive disease caused by mutation in the gene for the mito DNA polymerase POLG

Question 6

Leber’s hereditary optic neuropathy

Answer 6

Homoplasmic pattern
Can be heteroplasmic leading to variable expression
-sx–>rapid optic nerve death and blindness
-caused by a point mutation of gene and thereby affecting NADH dehydrogenase subunit ND4 in complex I of ETC