Mitochondrial disease with chronic progressive external ophthalmoplegia: clinical analysis of 19 cases

Mitochondrial myopathy is the commonest morphological diagnosis in the patients with the syndrome of chronic progressive external ophthalmoplegia. This syndrome consists of a group of clinically heterogeneous disorders. However, systemic analysis on clinical ground is still inexplicably lacking in Chinese.

Nineteen patients, who fulfilled the following two criteria, were collected and systematically analyzed on clinical ground. 1. Chronic progressive external ophthalmoplegia, characterized by chronic and progressive ptosis and limitation of eyeball movements, was the earliest and dominant clinical syndrome. 2. The mitochondria abnormalities were the only morphological changes on the limb muscle.

All patients were clinically classified into three groups. Twelve cases without extra-skeletal involvement were categorized as simple ocular myopathy; 5 cases as ophthalmoplegia plus syndrome because of the associated extra-skeletal dysfunction(s); and 2 cases as Kearns-Sayre syndrome according to the conventional triad (onset before 20 years of age, ophthalmoplegia, pigmentary degeneration of the retina) with at least one of three other major manifestations (heart block, CSF protein over 100 mg/dl, cerebellar syndrome).

The identification of the defects at the DNA level and determination of the phenotypic expression with basic biochemical methods as well as mitochondria DNA analysis are fundamental for more rational classification of mitochondrial myopathy. However, the classification, based on clinical criteria alone, may give the clinicians the convenience in the follow-up management of the non-skeletal disorders for an individual patient. Importantly, some of these disorders are life-threatening but treatable.