The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

Case Studies: Unexplained Dyspnea Connected with Neurologic Disorders

Fernando Martinez MD, John J. Wald MD, Monday, December 8, 1997.

Two patient histories will be summarized, illustrating how pulmonary exercise testing was useful in determining the diagnosis of metabolic/mitochondrial myopathy.

Case 1. KK was a 29 year old woman runner and body builder who noted rapidly progressive dyspnea, muscle weakness, and fatigue. One month after symptom onset she was unable to climb one flight of stairs. Dyspnea limited walking to approximately 10 meters before requiring rest. Initial PFTs: FVC of three liters (72% predicted). Exercise testing: O_{2} consumption 64% predicted, anaerobic threshold less than 50% predicted O_{2} consumption.

On the basis of the clinical history and exercise testing, muscle biopsy was performed, revealing abnormalities of lipid metabolism (accumulation of lipid and low intra-muscular carnitine) as well as markedly reduced mitochondrial oxidative function. Supplementation with co-enzyme Q_{10} and carnitine lead to dramatic improvement in function, normalization of strength, and improvement in FVC to 4.1 liters (104% predicted) which persists to date, nearly 3 years since initial diagnosis.

Case 2. JM was a 28 year old man evaluated for life-long spells of unconsciousness after exertion, thought to be seizures. Strength was normal, but unconsciousness and marked tachycardia and tachypnea (with gradual return to normal consciousness over 15 minutes) could be readily reproduced (video of JM exercising will be shown). During minimal aerobic exercise, lactic acid increased from 1 to 15 mEq/L (normal range 0.5 to 2, even during light exercise). Exercise testing confirmed peripheral O_{2} utilization defect (results will be reviewed).

Further evaluation revealed markedly abnormal muscle with mitochondrial accumulation, abnormal mitochondrial inclusions, but normal enzymatic function (as can be measured). Treatment trials have lead to no improvement to date.

AARC 50th Anniversary, December 6 - 9, 1997, New Orleans, Louisiana.

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