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An adolescent presents to your pediatrics clinic with fatigue. Her parents think she just doesn't like gym class, but she truly has exercise intolerance, myalgias, and poor endurance. On exam, you note muscle swelling and weakness after brief periods of intense isometric exercise. However, after a short break, the patient can resume physical activity without significant symptoms. Over the next few visits, you check CKs and they are always elevated; she also has intermittent myoglobinuria.

Challenge: What's the autosomal recessive disease described here?

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