FUNCTIONAL AND HISTOLOGIC PICTURE OF STEROID-INDUCED MYOPATHY IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

The functional and histologic picture of steroid-induced myopathy was systematically examined in eight patients with chronic obstructive pul monary disease (COPD) and compared with control patients with COPD mat ched for age, sex, and degree of airflow obstruction. Steroid-induced myopathy was associated with severe peripheral muscle weakness, quadri ceps force being 23 +/- 14 versus 71 +/- 23% in control patients with COPD (p < 0.001). in addition, clear ventilatory muscle weakness was p resent. PImax was 37 +/- 15 versus 67 +/- 24% in control patients (p < 0.007), and PEmax averaged 34 +/- 10 versus 74 +/- 23% (p < 0.001). V ital capacity tended to be slightly reduced compared with that in cont rol patients (69 +/- 21 versus 80 +/- 16%, p = 0.11). The only biochem ical abnormalities associated to steroid-induced myopathy were a moder ately increased lactic dehydrogenase level (697 +/- 301 versus 421 +/- 128 IU/L, p < 0.001) and an increased creatine excretion in 24-h urin e (990 +/- 609 versus 159 +/- 219 mg/24 h, p < 0.001). On quadriceps b iopsy steroid-induced myopathy was characterized by increased variatio n in diameter of fibers, with several angular atrophic fibers and diff use necrotic and basophilic fibers. In addition, increased amount of c onnective tissue in between fibers and increased number of subsarcolem mal and central nuclei were present. On ATPase stain diffuse fiber atr ophy predominantly affecting fast fibers was present, but there was no indication that atrophy was confined to type IIb fibers in contrast t o conventional thinking. On follow-up, survival of patients with stero id-induced myopathy was reduced in comparison with control patients wi th COPD with similar degree of airflow obstruction (p < 0.025).