Selenoprotein biosynthesis defect causes progressive encephalopathy with elevated lactate.

OBJECTIVE: We aimed to decipher the molecular genetic basis of disease in a cohort of children with a uniform clinical presentation of neonatal irritability, spastic or dystonic quadriplegia, virtually absent psychomotor development, axonal neuropathy, and elevated blood/CSF lactate. METHODS: We performed whole-exome sequencing of blood DNA from the index patients. Detected compound heterozygous mutations were confirmed by Sanger sequencing. Structural predictions and a bacterial activity assay were performed to evaluate the functional consequences of the mutations. Mass spectrometry, Western blotting, and protein oxidation detection were used to analyze the effects of selenoprotein deficiency. RESULTS: Neuropathology indicated laminar necrosis and severe loss of myelin, with neuron loss and astrogliosis. In 3 families, we identified a missense (p.Thr325Ser) and a nonsense (p.Tyr429*) mutation in SEPSECS, encoding the O-phosphoseryl-tRNA:selenocysteinyl-tRNA synthase, which was previously associated with progressive cerebellocerebral atrophy. We show that the mutations do not completely abolish the activity of SEPSECS, but lead to decreased selenoprotein levels, with demonstrated increase in oxidative protein damage in the patient brain. CONCLUSIONS: These results extend the phenotypes caused by defective selenocysteine biosynthesis, and suggest SEPSECS as a candidate gene for progressive encephalopathies with lactate elevation.

Infant stroke and beta-2-glycoprotein 1 antibodies: six cases.

UNLABELLED: The binding of autoimmune anticardiolipin antibodies to phospholipid has been shown to require a plasma cofactor, beta-2-glycoprotein 1 (beta2-GPI). Antibodies against beta2-GPI are associated with both venous and arterial thrombosis in adults and have been suggested as a new antiphospholipid syndrome marker. We present six children with cerebral thrombosis at the age of 0-12 months, who had IgG antibodies to beta2-GPI (titers 26, 29, 31, 39, 101 and 109 SGU, when 20 SGU was the cut-off). In at least four patients, the conventional antiphospholipid markers (lupus anticoagulant and IgG and IgM anticardiolipin) were negative. All six children had normal results in the other routine thrombophilia assays (thrombin time, antithrombin, protein C, protein S, factor V Leiden mutation, prothrombin mutation). CONCLUSION: the anti-beta-2 glycoprotein 1 assay, requiring only 5 microl serum, may be a useful addition to antiphospholipid-antibody diagnostics in cases of paediatric stroke.