PMC5395678_01
(A) Patient A1 at various ages. The video demonstrates orolingual and facial myoclonus.. (B) Patient A1 at various ages. The video demonstrates limb myoclonus, abdominal myoclonus and widespread polymyoclonus. Towards the end of the video distal choreoathetoid movements are also present in the upper limbs.. (C) Patient A2 at approximately 3 months of age. The video demonstrates myoclonus in the right arm and orolingual myoclonus.
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The deep grey matter appeared normal with no evidence of cortical dysplasia (Figure 1A). A computed tomography (CT) head scan showed tiny non-specific foci of calcification in the basal ganglia (Figure 1B). However, a repeat MRI scan at 3 years 10 months showed atrophy of the lateral aspects of the cerebellar hemispheres and symmetrical signaling abnormalities (Figure 1C). Using these criteria, two heterozygous variants confirmed by Sanger sequencing were identified in TBC1D24 (Supplementary Figure 1): 1) a previously reported missense change c.457G>A (p.Glu153Lys; rs376712059) and 2) a previously unreported frameshift mutation, c.545del (p.Thr182Serfs*6) predicted to cause nonsense-mediated RNA decay or result in a truncated protein.
Magnetic Resonance Imaging Features in Sibship with TBC1D24 Mutations. (A) MRI brain scan (Axial T2-weighted) of A1 age 19 months showing underdevelopment of the frontal and temporal lobes. (B) CT head scan of A1 20 months showing small non-specific foci of calcification within the basal ganglia. (C) MRI head scan (Coronal T2-weighted) of A2 at 3 years 10 months showing symmetrical signal abnormalities and atrophy of the lateral aspects of the cerebellar hemispheres.
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A few myoclonias were more hypersynchronous, approximately 40-60 ms in duration (Supplementary Figure 2).