Abstract

Purpose: To present an unusual case of MELAS with initial symptomatic onset in a 28-year-old female recently diagnosed with type 1 diabetes mellitus.
Introduction: Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) is a mitochondrial DNA inherited disorder that presents primarily with neurologic symptoms, such as visual loss migraine-like headaches and stroke like episodes not corresponding to any specific vascular territory. Most cases of MELAS present in childhood or before the age of 20. We present a case of MELAS with initial presentation at 28 years old in a patient with recently diagnosed type 1 diabetes mellitus with medication noncompliance.
Case summary: A 28-year-old Caucasian right-handed female presented to the emergency room with sudden-onset occipital headache and vision loss. In the ER, she experienced a tonic-clonic seizure responsive to lorazepam. Neurological exam revealed left homonymous hemianopsia. Neuroimaging found evidence of a right inferior temporal/occipital lesion, initially thought to be consistent with posterior reversible encephalopathy syndrome. Repeat imaging and further laboratory workup was indicated to evaluate for metabolic etiologies given her persistence of symptoms and diabetes history. Serum lactate was then found to be markedly elevated. A molecular genetics report demonstrated that the patient was hetero-plasmic in the MT-TL1 gene (37.6%) for a sequence variant designated m.3243A>G. These results confirmed the final diagnosis of MELAS.
Conclusion: Though rare, MELAS may present in adulthood, as exhibited in this patient. In these cases, measurement of lactate and genetic studies significantly contribute to the final diagnosis. Furthermore, concurrent metabolic comorbidities such as recently diagnosed type 1 diabetes strengthen the diagnostic consideration for MELAS.

Keywords: MELAS; Lactic acidosis; MT-TL1gene

Abbreviations:MELAS: Mitochondrial Encephalopathy with Lactic Acidosis and Stroke-like Episodes; CSF: Cerebrospinal Fluid; PRES: Posterior Reversible Encephalopathy Syndrome; tRNA: Transfer RNA