Diseases

Question 1

MERRF

Answer 1

Myoclonic Epilepsy associated with Ragged Red Fiber).
A to G mutation at nt 8344 80-90%
Mutation in mitochondrial tRNA lysine
a. Variable symptoms among maternal relatives correlate to OXPHOS deficiency
b. Sequential appearance of: Electrophysiological aberrations of CNS,
Mitochondrial myopathy, neurosensory deafness, Myoclonic epilepsy,
Progressive dementia, Cardiac insufficiency, renal dysfunction
c. Severity of phenotype depends on percentage of mutant mtDNA and age
d. Ragged Red Fiber in diagnosis.
e. Mutations in tRNA genes.

Question 2

MELAS

Answer 2

Mitochondrial Encephalopathy with Lactic Acidosis and
Stroke-like episodes).
Mutation in tRNAs for leucine and glutamine. Mutations in Complex I ND genes
a. Symptoms overlap with MERRF, but mainly due to CNS defects1, including
seizures, hemiparesis, hemianopsia, cortical blindness, and episodic vomiting.
b. Mutations in tRNA and NAD dehydrogenase (ND)- NADH DH genes.

Question 3

LHON

Answer 3

Leber Hereditary Optic Neuropathy = Leber Optic Atrophy)
Mutations in Complex I ND genes
a. Mid-life, acute or subacute, painless, central vision loss leading to central
scotoma.
b. Mutations in ND genes.

Question 4

KSS

Answer 4

(Kearns-Sayre Syndrome) / CPEO (OMIM# 530000: Chronic Progressive
External Ophthalmoplegia).
a. Variable symptoms, but virtually all have paralysis of eye muscles
(ophthalmoplegia)
b. Deletion mutations in mitochondrial genome.

Question 5

MNGIE

Answer 5

(mitochondrial
neurogastrointestinal encephalomyopathy) (mutations in TP, encoding thymidine
phosphorylase)

Question 6

PEO

Answer 6

(progressive external ophthalmoplesia) (mutations in

ANT1, twinkle, and POLG)

Question 7

Alpers / Ataxia

Answer 7

(mutations in POLG)

Question 8

Mutations affecting ETC functions

Answer 8

myoclonic epilepsy, leukodystrophy, Leigh

disease, ataxia, seizures, cardiomyopathy, and encephalopathy.