Nine newly identified individuals refine the phenotype associated with MYT1L mutations.

Both point mutations and deletions of the MYT1L gene as well as microdeletions of chromosome band 2p25.3 including MYT1L are associated with intellectual disability, obesity, and behavioral problems. Thus, MYT1L is assumed to be the-at least mainly-causative gene in the 2p25.3 deletion syndrome. Here, we present comprehensive descriptions of nine novel individuals bearing MYT1L mutations; most of them single nucleotide variants (SNVs). This increases the number of known individuals with causative deletions or SNVs of MYT1L to 51. Since eight of the nine novel patients bear mutations affecting MYT1L only, the total number of such individuals now nearly equals the number of individuals with larger microdeletions affecting additional genes, allowing for a comprehensive phenotypic comparison of these two patient groups. For example, 55% of the individuals with mutations affecting MYT1L only were overweight or obese as compared to 86% of the individuals with larger microdeletions. A similar trend was observed regarding short stature with 5 versus 35%, respectively. However, these differences were nominally significant only after correction for multiple testing, further supporting the hypothesis that MYT1L haploinsufficiency is central to the 2p25.3 deletion phenotype. Most importantly, the large number of individuals with MYT1L mutations presented and reviewed here allowed for the delineation of a more comprehensive clinical picture. Seizures, postnatal short stature, macrocephaly, and microcephaly could be shown to be over-represented among individuals with MYT1L mutations.

[On the fast track to diagnosis : Recommendations for patients without a diagnosis]. / Kurze Wege zur Diagnose : Eine Handlungsempfehlung für Patienten ohne Diagnose.

BACKGROUND: Patients, who have spent many years without a proper diagnosis present an extraordinary problem to health care providers and to the healthcare system as a whole. A long 'diagnostic journey' increases the risk of disease chronification, as well as the number of therapy attempts, which could lead to iatrogenic impairment. New resources and specialized health care departments are being developed to help and support this patient group. One example of such department is the Interdisciplinary Competence Unit for Patients without a Diagnosis at the center for rare diseases in Bonn (ZSEB), Germany. OBJECTIVE: To shed light on the current health care management of patients without a diagnosis and to present an established directive to optimize the care for this patient group, as practiced at the InterPoD. METHODS: Showcase of directives and advice for the health care management of long-term patients without a diagnosis. RESULTS: Sociodemographic and clinical characteristics based on the treated patient collective at the InterPoD along with their directives, from the years 2014 to 2016. DISCUSSION: The descriptive statistics and the increasing number of treated patients are a first indication of the usefulness of InterPoD-related processes.

De novo nonsense and frameshift variants of TCF20 in individuals with intellectual disability and postnatal overgrowth.

Recently, germline variants of the transcriptional co-regulator gene TCF20 have been implicated in the aetiology of autism spectrum disorders (ASD). However, the knowledge about the associated clinical picture remains fragmentary. In this study, two individuals with de novo TCF20 sequence variants were identified in a cohort of 313 individuals with intellectual disability of unknown aetiology, which was analysed by whole exome sequencing using a child-parent trio design. Both detected variants - one nonsense and one frameshift variant - were truncating. A comprehensive clinical characterisation of the patients yielded mild intellectual disability, postnatal tall stature and macrocephaly, obesity and muscular hypotonia as common clinical signs while ASD was only present in one proband. The present report begins to establish the clinical picture of individuals with de novo nonsense and frameshift variants of TCF20 which includes features such as proportionate overgrowth and muscular hypotonia. Furthermore, intellectual disability/developmental delay seems to be fully penetrant amongst known individuals with de novo nonsense and frameshift variants of TCF20, whereas ASD is shown to be incompletely penetrant. The transcriptional co-regulator gene TCF20 is hereby added to the growing number of genes implicated in the aetiology of both ASD and intellectual disability. Furthermore, such de novo variants of TCF20 may represent a novel differential diagnosis in the overgrowth syndrome spectrum.