"Drop attacks" as first clinical symptoms in a child carrying MTTK m.8344A>G mutation

We describe a child with dyslexia and difficulty in school who, at the age of 13 years, began to suffer from several head injuries resulting from falls of uncertain cause. Two years later, the patient developed symptoms of a severe mitochondrial disorder (involving bulbar-pyramidal paralysis, ophthalmoplegia, and hyperlactatemia) that coincided with VPA administration. Brain MR imaging revealed rapidly developing Leigh syndrome (LS), and muscle biopsy showed ragged blue fibres (RBF). A diminished expression of the E1α subunit of pyruvate dehydrogenase was found in muscle homogenate (signal 28.7% of normal). The accurate diagnosis of mitochondrially inherited LS (MILS) and the identification of an almost homoplasmic m.8344G>A mutation in the MTTK gene was delayed due to an initial incorrect diagnosis of epilepsy, misdiagnosis of neuroinfection, and failure to note LS on the first brain MRI. Periods of exacerbation or improvement were observed in association with the administration of certain drugs or procedures (VPA administration or intensive rehabilitation associated with worsening; ketogenic diet associated with remission). However, the random association of these factors with natural disease fluctuations cannot be excluded.

1) To improve the early detection of mitochondrial disorder, we recommend screening for mtDNA (and nDNA) mutations in all patients with LS present on brain MRI. 2) Brain MRI protocols should include diffusion-weighted and T2-weighted imaging, and LS-like changes should be analysed by a neuroradiologist experienced in the field. 3) Additional controlled studies are urgently needed to assess the causal relationship between management strategies and the natural history of the disease. Until the association between VPA and disease exacerbation can be ruled out, VPA should be avoided in patients with these symptoms unless the mitochondrial disorder has been excluded.