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A6770 - Mitochondrial Myopathy Presenting in Late Adulthood: A Rare Occurrence
Author Block: H. Hadid; Henry Frod Health System, Detroit, MI, United States.
Background: Mitochondrial diseases are rare hereditary diseases that may be progressive and fatal. Muscle involvement in mitochondrial diseases is common, and involvement of respiratory muscle may prove fatal. This spectrum of diseases is usually passed on from mother to female children, and typically presents before age 20. Presenting late in adulthood is exceedingly rare, and only very few case reports have been described. Case: A 66 year old female is admitted to the hospital with shortness of breath and progressive weakness over the last few weeks. The patient is adopted and has no known family history, and medical history is only positive for recent diagnosis of COPD. This diagnosis was made clinically due to new hypercapnea noted on outpatient ABG along with her subjective symptoms of dyspnea. Prior pulmonary function testing revealed moderately impaired FEV1 with a normal FEV1/FVC ratio, and moderate diffusion impairment. She also had decreased respiratory muscle forces on the complete PFTs she had prior to admission. Initial ABG revealed a pCO2 of > 120 with a pH of 7.30. Her CT revealed mild emphysema. Given her normal BMI, lack of sleep apnea risk factors, and lack of explanation to her profound hypercapnea that only developed over few weeks, there was a concern for myopathy so she was referred to neurology. An extensive workup for myopathy including a long panel of antibodies was done and only aldolase, CPK, and LDH came back mildly elevated. EMG was done showing myonecrosis, and this was followed by a deltoid muscle biopsy. The biopsy was suggestive for mitochondrial myopathy with ragged red fibers and more than 20% COX-negative fibers. Conclusion: Although common things are common, it is important to realize that when more than one piece of the puzzle does not fit, an alternative diagnosis must be sought. This patient had weakness over weeks and newly discovered hypercapnea, not purely explained by PFTs. In addition, her PFTs were more suggestive of restrictive lung disease and decreased respiratory muscle strength, rather than COPD. Although rare, diagnoses such as mitochondrial myopathy must be considered when common diseases do not explain the clinical picture.