Respiratory failure in nemaline myopathy.

Four patients with nemaline myopathy, 1 with the severe infantile form and 3 with the benign congenital (classical) form, exhibited significant respiratory problems. In the patient with the severe infantile form, respiratory failure paralleled the generalized muscle weakness, whereas the 3 patients with the benign infantile form suddenly developed respiratory failure while still ambulant. Polysomnographic studies performed on 2 patients revealed that apnea or irregular thoracic movements occurred only during rapid eye movement sleep, when hypercapnia was also demonstrated on serial transcutaneous partial O2 and partial CO2 monitoring. A discrepancy between motor ability and respiratory involvement probably is not uncommon in patients with the moderate congenital form of nemaline myopathy. Clinicians must always be alert to respiratory failure when monitoring patients with nemaline myopathy.