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Título

Adult-onset MELAS: what is the best way to investigate?

RESUMO

CASE PRESENTATION:
Female patient, 41 years old, with a previous history of non-migraine headache and cramps during exercise, presented, at the age of 36, a sudden change in consciousness associated with reduced visual acuity on the right, auditory and visual hallucinations, with complete recovery in two days. . Here, she was diagnosed with a psychiatric illness. After four years, she had a new episode, but now with associated right hemiparesis. Within two months, she recovered, but remained with some cognitive sequelae (mainly memory and executive dysfunction). After months, she had a new crisis, now with left hemiparesis, which was initially treated as herpetic encephalitis. His exams revealed an increase in CPK, an increase in CSF lactate (despite normal cellularity and proteinorrhea) and cranial resonance with extensive DWI / FLAIR lesion in the occipital, temporal and frontal regions on the right, not respecting vascular territory and without marked hyposignal in the ADC map, in addition to lactate peak spectroscopy. Panel of autoantibodies, electroneuromyography, echocardiogram, CT of the abdomen, thorax and pelvis without alterations. Due to the clinical suspicion of mitochondrial disease, a molecular study was carried out, collected by oral swab, aimed at the variants most associated with MELAS. This showed the presence, in heteroplasmy (in 36% of the readings performed), of the pathogenic variant m.3243A>G in the MT-TL1 gene, the most associated with this syndrome, confirming the patient's diagnosis.
DISCUSSION:
Adult-onset MELAS, especially after the age of 20 years, is considered very uncommon, which leads to a delay in diagnosis by being confused with isolated psychiatric conditions or other causes of encephalitis. In cases where clinical suspicion is form, it is initially recommended to evaluate the variants in the MT-TL1 gene. The m.3243A>G variant is the one most associated with MELAS syndrome, and the degree of heteroplasmy in oral swab collection is in agreement with what has been previously reported. If it were low, due to the high clinical suspicion, one possibility would be to perform the analysis on epithelial cells by urine collection, since it is the sample that shows the highest percentages of heteroplasmy, among those of easy access.
FINAL COMMENTS
In adult-onset forms, diagnostic delay of MELAS is common. In addition, collection by blood or oral swab is the most performed, although urinary analysis has a higher diagnostic yield.

Palavras Chave

MELAS syndrome; MT-TL1; m.3243A>G