Pre-test general part 1

You are examining a patient through the mitochondrial clinic. The 4-year boy presents with infantile onset of symptoms, which include myopathy and liver failure. Testing reveals mutations in the gamma polymerase gene. How do you counsel this family regarding inheritance?

• X-linked dominant

• Sporadic

• Maternal

• Autosomal recessive

A brother and sister presented in early infancy with moderate developmental delay and a severe seizure disorder. No other family members are affected. Muscle biopsy in the boy supports the presence of a mitochondrial disorder. The recurrence risk in future siblings is most likely:

• 25%

• 50%

• Very high (likely ~80%)

• Cannot determine from this information

The co-existence of 2 or more mtDNA types in the same cell, tissue and organism is known as:

• Homoplasmy

• heteroplasmy

• mosaicism

• mutation

A boy with an unknown mitochondrial disease and a negative family history is how likely to have an affected child with the same condition:

• Essentially never (unless in a consanguineous union)

• Quite unlikely, but possible in the rare case of autosomal dominant inheritance

• Estimated 25%

• 0-100% - unable to determine

The bottleneck phenomenon results in:

• The absence of clinical disease until mutant mtDNA levels reach a certain level.

• Sporadic disease in the case of a large mtDNA deletion.

• Varying proportions of mutant heteroplasmy among tissues in an affected individual.

• Often drastically varying proportions of mutant heteroplasmy among individuals in a family segregating a mtDNA mutation

A child is suspected of having a mitochondrial disease based upon clinical, laboratory and pedigree-based information. \"Standard mtDNA analysis\" was negative. Which of the following statements is most accurate:

• The patient does not have a mitochondrial disorder.

• The patient probably has a nuclear-encoded mitochondrial disorder (X-linked or autosomal dominant).

• Standard mtDNA testing is very insensitive, and mtDNA disease is present.

• Could be any of the above; careful evaluation and a very detailed pedigree are indicated.

In mitochondrial disease, exercise can:

• Precipitate rhabdomyolysis (muscle breakdown)

• Increase strength and endurance

• Both; moderate and careful training are key

• None of the above

Migraine and multiple strokes or stroke-like episodes is most consistent with:

• Kearns-Sayre syndrome

• Leigh disease

• MELAS

• MERRF

Mitochondrial disease is frequently:

• progressive

• intermittent

• static

• all of the above

Which of the following is considered a primary defect occurring by 8 to 10 weeks of gestation?

• Web neck

• Cleft lip

• Contracture

• Club feet