A Case of Adult-onset MELAS as a Rapidly Progressive Dementia: Variant of Unknown Significance and the Importance of Neuropathologic Confirmation
Molly Wiggins1, Nikita Jain1, Jessica Tate2, Amelia Kirby 2, Dennis Dickson3, James Bateman2
1Neurology, Atrium Health Wake Forest Baptist, 2Atrium Health Wake Forest Baptist, 3Mayo Clinic
Objective:
To highlight the importance of adult-onset mitochondrial disorders in the differential diagnosis of rapidly progressive dementias. We present a case of mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) that was diagnosed at autopsy.
Background:
MELAS is one of the most common mitochondrial diseases and is characterized by recurring episodes of encephalopathy, myopathy, headaches, seizures, and focal neurological deficits. MELAS typically manifests in childhood and has a progressive course. Less commonly, MELAS presents in adults with a rapidly progressive dementia.
Results:
A 43-year-old female presented for admission with a 4-month history of rapidly progressive neurological decline. Symptoms began acutely with short-term memory and speech difficulties followed by rapidly worsening dysarthria, emotional lability, weakness, and spasticity. Work-up included multiple brain MRIs, which showed shifting areas of restricted diffusion with both cortical and extensive white matter involvement on a background of progressive cerebral volume loss. CSF analysis and an extensive metabolic work-up were unrevealing, apart from one abnormal lactic acid during a previous hospitalization. Whole exome sequencing was performed, which showed a variant of unknown significance in the SDHA gene. Other mutations in this gene have been associated with mitochondrial neurodegeneration. The implication of this finding was initially unclear. A brain biopsy was performed that showed spongiform changes and gliosis, which raised concern for Creutzfeld-Jakob Disease, although CSF and brain MRI were inconsistent with this diagnosis. Ultimately, the patient passed away less than a month after discharge. A brain autopsy was performed and demonstrated multifocal infarct-like cortical lesions, consistent with MELAS, with no evidence of prion disease.
Conclusions:
Adult-onset mitochondrial disease is a rare but important consideration in the differential for rapidly progressive dementia. This case highlights the importance of a broad differential diagnosis in rapidly progressive dementias, especially when atypical features are present, and demonstrates the critical role of autopsy in these cases.