Low blood heteroplasmy-rate may cause late-onset MELAS☆☆☆★

Letter to the Editor The interesting article by Sunde et al. about a 54 yo female with MELAS due to the m.3243ANG mutation with a blood heteroplasmyrate of 31% and manifesting with recurrent stroke-like episodes(SLEs), tonic-clonic seizures, migraine, hypothyroidism, short stature, fatigability, and hearing-loss [1] raises the following comments and concerns. For epilepsy the patient was initially treated with levetirazetam, phenytoin, and lamotrigine [1]. Which was the daily dosage of each of these antiepileptic drugs(AEDs)?Whywere three AEDs applied for prophylaxis?Whichwere the serum levels of these AEDs? From phenytoin it is well-known that it is mitochondrion-toxic [2].Whywas it nonetheless given?Did seizures occur shortly before, during, or long after a SLE? Was confusion after starting AEDs attributable to phenytoin? Clonazapan is no AED. Do the authors mean clonazepam? A heteroplasmy-rate of 31% in lymphocytes is low. Was heteroplasmy-rate determined also in other tissues, such as hair follicles, buccal mucosa, urinary epithelial cells, or muscle? Were heteroplasmy-rates higher in other tissues? Heteroplasmy-rates are reported to increase over time in post-mitotic tissues [3]. Were heteroplasmy-rates repeatedly determined during the disease course? Did they indeed increase over time? SLEs typically go along with a stroke-like lesion on cerebral MRI(cMRI) [4]. Did the patient ever undergo a cMRI during a SLE? Was a characteristic vasogenic edema not concurring within a vascular territory seen in the acute stage?