Dystonia with aphonia, slow horizontal saccades, epilepsy and photic myoclonus: a novel syndrome?

Expanding the phenotype of NEDAMSS with a psychiatric perspective: analysis of a new case, and a systematic review of the literature

Pathogenic variants in the IRF2BPL gene are associated with neurodevelopmental disorders with varying degrees of regression, loss of speech and epilepsy. The phenotype is also known as Neurodevelopmental Disorder with regression, Abnormal Movements, loss of Speech, and Seizures (NEDAMSS). The motor symptoms of this disorder share significant phenotypical characteristics with catatonia, a severe neuropsychiatric psychomotor syndrome. The objective of this article is to expand the knowledge on the presentation of NEDAMSS with a focus on psychiatric symptoms including catatonia. A systematic review of 32 case presentations of NEDAMSS, and a novel case report of a patient with NEDAMSS, exhibiting multiple psychiatric symptoms, including catatonia are presented. Psychiatric symptoms and disorders including affective disorders, psychotic symptoms, catatonia, and developmental disorders are reported in one third of the reviewed cases. Reported effects of pharmacological treatment on motor symptoms of NEDAMSS are very limited. Our case presents improvement in motor symptoms originally attributed to NEDAMSS, after treatment with Lorazepam following diagnosis with catatonia. Patients with NEDAMSS may present with both neurological and psychiatric symptoms. The clinical presentation of NEDAMSS motor symptoms and catatonia have similarities and thus poses significant challenges to the diagnostic process, with risk of incorrect or delayed treatment. The limited experience and the complex phenotype of NEDAMSS complicates pharmacological treatment and encourages caution, especially with the use of antipsychotic drugs in the presence of possible catatonic symptoms.

IRF2BPL as a novel causative gene for progressive myoclonus epilepsy

IRF2BPL has recently been described as a novel cause of neurodevelopmental disorders with multisystemic regression, epilepsy, cerebellar symptoms, dysphagia, dystonia, and pyramidal signs. We describe a novel IRF2BPL phenotype consistent with progressive myoclonus epilepsy (PME) in three novel subjects and review the features of the 31 subjects with IRF2BPL-related disorders previously reported. Our three probands, aged 28-40 years, harbored de novo nonsense variants in IRF2BPL (c.370C > T, p.[Gln124*] and c.364C > T; p.[Gln122*], respectively). From late childhood/adolescence, they presented with severe myoclonus epilepsy, stimulus-sensitive myoclonus, and progressive cognitive, speech, and cerebellar impairment, consistent with a typical PME syndrome. The skin biopsy revealed massive intracellular glycogen inclusions in one proband, suggesting a similar pathogenic pathway to other storage disorders. Whereas the two older probands were severely affected, the younger proband had a milder PME phenotype, partially overlapping with some of the previously reported IRF2BPL cases, suggesting that some of them might be unrecognized PME. Interestingly, all three patients harbored protein-truncating variants clustered in a proximal, highly conserved gene region around the "coiled-coil" domain. Our data show that PME can be an additional phenotype within the spectrum of IRF2BPL-related disorders and suggest IRF2BPL as a novel causative gene for PME.

Neurological Phenotypes of IRF2BPL Gene Variants: A Report of Four Novel Variants

IRF2BPL gene variants have recently been associated to developmental disability and epilepsy in children and movement disorders in adults. So far, only few cases have been reported; here we present four novel cases identified by exome sequencing, while investigating developmental delay, adult-onset cerebellar ataxia or regression.