Discussion and Conclusion
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is the most common maternally-inherited mitochondrial disorder, which usually becomes symptomatic before the age of 40 years8. MELAS is characterized by stroke-like episodes, seizures, dementia, encephalopathy, lactic acidosis and also RRFs on muscle biopsy9.
Previous studies reporting cases of MELAS have shown specific characteristics on brain MRI imaging of these patients. Transient stroke-like lesions have been reported in these patients, typically affecting gray matter without being restricted to vascular areas. Involvement of white matter has also been observed in MELAS, being more distinguished in periventricular white matter and centrum semiovale. All the previously reported cases of MELAS have reported a fluctuating characteristic for the lesions observed in the brain MRI10.
The case we report here suffered from progressive cognitive decline, encephalopathy, seizures and stroke-like episodes, being compatible with the previously reported cases of MELAS. Nevertheless, this patient had some unique features, never reported in cases of MELAS so far, leading to mismanagement. Since structural heart diseases are more common in young adults with stroke11; to rule out the presence of any heart diseases, echocardiography was performed in our patient and patent foramen ovale (PFO) was discovered and confirmed with trans-esophageal echocardiography (TEE). This finding was first misdiagnosed as the reason for the patient’s symptoms, medication was prescribed according to this finding and further investigations were postponed to his next admissions. Despite treatment with anticoagulant, the patient had had another stroke, so investigation was done again to find a cause and led to diagnosis of MELAS.
Our literature review revealed no evidence of existing PFO in MELAS cases. Johnson et al. described a MELAS patient in their case report who was once diagnosed with PFO in echocardiography which was later ruled out with TEE. The only reason they could find for the incidence of stroke in their patient was MELAS syndrome13.
Another unique presentation in our patient was the pattern of ischemia lesions being different from the previously reported fluctuating characteristic of the lesions on MRI, lesions had a progressive pattern in this patient and every time he was admitted, new lesions were added to the old ones, without disappearing of previous lesions.
In conclusion, this is the first reported case of MELAS syndrome with PFO and progressive pattern of ischemic lesions on brain MR imaging. The presence of PFO has led to mismanagement and late diagnosis in this patient. For this reason further investigations are recommended to rule out PFO in MELAS cases presenting by stroke-like symptoms.
All procedures performed in this study were in accordance with the ethical standards of Shahid Beheshti Medical University research ethics committee and with the 1964 Helsinki Declarations and its later amendments. The study was approved by the Bioethics Committee of the Medical University of the Medical University of Shahid Beheshti.