A 23-year-old man is being evaluated for myoclonic epilepsy of recent onset. The episodes are short-lived and triggered by startle. Physical examination reveals proximal muscle weakness. Gomori trichrome stain of a muscle biopsy specimen shows muscle fibers with a blotchy red appearance. No family history is available because the patient is adopted. What is the probability that this patient's one offspring will inherit the disease?

Question

A 23-year-old man is being evaluated for myoclonic epilepsy of recent onset.  The episodes are short-lived and triggered by startle.  Physical examination reveals proximal muscle weakness.  Gomori trichrome stain of a muscle biopsy specimen shows muscle fibers with a blotchy red appearance.  No family history is available because the patient is adopted.  What is the probability that this patient's one offspring will inherit the disease?

Quizplus · Accepted Answer

Eductional Objective: "Red ragged" muscle fibers are seen in mitochondrial diseases.  Muscle fibers have this appearance because abnormal mitochondria accumulate under the sarcolemma.  Mitochondrial diseases show maternal inheritance.

A 23-Year-Old Man Is Being Evaluated for Myoclonic Epilepsy of Recent