A 19-year-old girl is being tested for new-onset generalized tonic-clonic seizures. She has also had unpredictable jerks of her arms and legs, as well as occasional muscular weakness, for several years. The girl has other family relatives who have identical symptoms. A neurological examination indicates a broad-based gait and diminished feeling in the lower limbs. A skeletal muscle biopsy reveals ragged, red-colored muscular fibers. Further investigation revealed that the patient's symptoms are caused by a mutation that affects extranuclear DNA. Which of the following pedigrees best describes this patient's family history? (The arrow points to the patient.)

Question

Quizplus · Accepted Answer

Eductional Objective: On muscle biopsy, mitochondrial dysfunction is commonly associated with myopathy, nervous system dysfunction, lactic acidosis, and ragged red fibers. Mitochondrial myopathies caused by mtDNA mutations are only inherited through the mother (ie, maternal inheritance). As a result, transmission happens only via afflicted females and never through men.

A 19-Year-Old Girl Is Being Tested for New-Onset Generalized Tonic-Clonic