Mitochondrial Myopathy in a heart transplant recipient: A case report

Aims: Mitochondrial myopathy (MM) is a phenotype of respiratory chain disease (RCD), a systemic disorder caused by mitochondrial DNA mutations. Cardiac involvement varies but may lead to metabolic cardiomyopathy. We present a patient who was diagnosed with MM following heart transplantation (HTx)

Case: A 23-year old male patient who suffered from severe heart failure diagnosed as being hypertrophic cardiomyopathy (HCM) underwent cardiac transplantation in 2007. Prior to HTx no clinical, pathological or biochemical signs suggestive of respiratory chain disease had been reported. The patient showed an unremarkable early post-Tx course with prompt improvement in exercise capacity. However, 15 months post HTx, he started to complain of weakness of the thigh muscles and exhaustion with shortness of breath at exertion. Creatine kinase levels were normal. Graft function remained unremarkable, acute cellular rejection was ruled out. Right-heart catheterization during exercise ruled out pulmonary hypertension but revealed increased lactate (19mmol/l) at minimal workload. Statins were withdrawn and immunosuppression changed to a calcineurin-inhibitor (CNI) free regimen of everolimus, mycophenolate mofetil, and low-dose prednisolone, to rule out CNI-induced myopathy. However, musle weakness aggrevated gradually and progressively. The neurological status was unremarkable; muscle biopsy was suggestive of a combined respiratory chain defect, with deficiency of complexes I and IV diagnosed by genetic testing. Due to a lack of established therapy and progressive clinical deterioration a trial with coenzyme Q was started but showed no effect. Instead a trial with high-dose bezafibrate (400mg b.i.d.) was initiated and caused considerable improvement of symptoms.

Conclusion: MM may mimic HCM and is a diagnostic and therapeutic challenge, especially in heart transplant recipients. Experimental therapy with high-dose bezafibrates has been successful in this case.