PMC9205445_01
Case presentation: clinical features of NUS1 and MEAD syndrome. The video shows the most relevant clinical features of a new case of myoclonus-epilepsy associated with a novel de novo missense variant of NUS1 (c.868C>T, p.R290C): speech is preserved; there is multifocal, mini-myoclonus of the face; eye movements only showed mild saccadic intrusion of pursuits; there is appendicular myoclonus involving the upper limbs, distally; there is no bradykinesia and only mild incoordination; there is action myoclonus that increases at target in both upper limbs; there is only mild appendicular ataxia and past-pointing; there is no stimulus-sensitive myoclonus; there is significant action myoclonus at approaching the paper with a pen and drawing a spiral; gait is narrow-based with no ataxia.
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V1
Here we summarize the most significant phenotypes (Figure 1).
NUS1 pathogenic variants and related phenotypes. The figure summarizes the pathogenic variants reported in the literature in the NUS1 gene, highlighting their position on the gene, and associated phenotype: ataxia (orange), ID (light blue), or both (green) with epilepsy (upper part of the figure) or without epilepsy (lower part of the figure). Myoclonus was reported in all the listed variants except for c.869G>A (p.Arg290His) (homozygous), and c.743delA (p.Asp248Alafs). The only reported homozygous variant associated with CDG is bolded. Protein domains are labeled. TM: transmembrane. The new variant found in this report (likely pathogenic) is highlighted by the red box.
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Brain MRI showed mild cerebellar atrophy (Figure 2).