Recurrent respiratory insufficiency and depressed ventilatory drive complicating mitochondrial myopathies.

Three patients with mitochondrial myopathies and progressive external ophthalmoplegia had repeated episodes of respiratory failure requiring assisted ventilation. Studies in these patients and asymptomatic family members, as well as a sporadic case of Kearns-Sayre syndrome, demonstrated markedly depressed ventilatory drive responses to hypoxia. In 2 patients, there was also decreased drive to hypercapnia. The reduced ventilatory drive appears to be due to an altered neural control system that may cause episodic life-threatening hypoventilation occurring especially in relation to surgery, sedation, or intercurrent infection.