Primary mitochondrial disease as a rare cause of unclear breathlessness and distinctive performance degradation – a case report

BACKGROUND: Primary muscular disorders (metabolic myopathies, including mitochondrial disorders) are a rare cause of dyspnea. We report a case of dyspnea caused by a mitochondrial disorder with a pattern of clinical findings that can be classified in the known pathologies of mitochondrial deletion syndrome. CASE PRESENTATION: The patient presented to us at 29 years of age, having had tachycardia, dyspnea, and functional impairment since childhood. She had been diagnosed with bronchial asthma and mild left ventricular hypertrophy and treated accordingly, but her symptoms had worsened. After more than 20 years of progressive physical and social limitations was a mitochondrial disease suspected in the exercise testing. We performed cardiopulmonary exercise testing (CPET) with right heart catheterization showed typical signs of mitochondrial myopathy. Genetic testing confirmed the presence of a ~ 13 kb deletion in mitochondrial DNA from the muscle. The patient was treated with dietary supplements for 1 year. In the course of time, the patient gave birth to a healthy child, which is developing normally. CONCLUSION: CPET and lung function data over 5 years demonstrated stable disease. We conclude that CPET and lung function analysis should be used consistently to evaluate the cause of dyspnea and for long-term observation.