No abstract

Summary Truncating variants in exons 33 and 34 of the SNF2-related CREBBP activator protein ( SRCAP ) gene cause the neurodevelopmental disorder (NDD) Floating-Harbor syndrome (FLHS), characterized by short stature, speech delay, and facial dysmorphism. Here, we present a cohort of 33 individuals with clinical features distinct from FLHS and truncating (mostly de novo ) SRCAP variants either proximal (n = 28) or distal (n = 5) to the FLHS locus. Detailed clinical characterization of the proximal SRCAP individuals identified shared characteristics: developmental delay with or without intellectual disability, behavioral and psychiatric problems, non-specific facial features, musculoskeletal issues, and hypotonia. Because FLHS is known to be associated with a unique set of DNA methylation (DNAm) changes in blood, a DNAm signature, we investigated whether there was a distinct signature associated with our affected individuals. A machine-learning model, based on the FLHS DNAm signature, negatively classified all our tested subjects. Comparing proximal variants with typically developing controls, we identified a DNAm signature distinct from the FLHS signature. Based on the DNAm and clinical data, we refer to the condition as “non-FLHS SRCAP -related NDD.” All five distal variants classified negatively using the FLHS DNAm model while two classified positively using the proximal model. This suggests divergent pathogenicity of these variants, though clinically the distal group presented with NDD, similar to the proximal SRCAP group. In summary, for SRCAP , there is a clear relationship between variant location, DNAm profile, and clinical phenotype. These results highlight the power of combined epigenetic, molecular, and clinical studies to identify and characterize genotype-epigenotype-phenotype correlations.

Whole‐exome sequencing has established IQSEC2 as a neurodevelopmental disability gene. The IQSEC2 variant phenotype includes developmental delay, intellectual disability, epilepsy, hypotonia, autism, developmental regression, microcephaly and stereotypies but is yet to be fully described. Presented here are 14 new patients with IQSEC2 variants. In addition to the established features, we observed: gait ataxia in 7 of 9 (77.8%), drooling in 9 of 14 (64.2%), early feeding difficulties in 7 of 14 (50%), structural brain abnormalities in 6 of 13 (46.2%), brachycephaly in 5 of 14 (35.7%), and scoliosis and paroxysms of laughter each in 4 of 14 (28.6%). We suggest that these are features of the IQSEC2‐related disorder. Gastrostomy requirement, plagiocephaly, strabismus and cortical blindness, each seen in 2 of 14 (14.3%), may also be associated. Shared facial features were noted in 8 of 14 patients, and shared hair patterning was identified in 5 of 14 patients. This study further delineates the IQSEC2 phenotypic spectrum and supports the notion of an emerging IQSEC2 syndrome. We draw parallels between the IQSEC2‐related disorder and the Angelman‐/Rett‐/Pitt‐Hopkins syndrome group of conditions and recommend the addition of IQSEC2 to epilepsy and developmental delay gene panels. We observed discordant phenotypes in monozygotic twins and apparent gonadal mosaicism, which has implications for recurrence risk counselling in the IQSEC2‐related disorder.

No abstract

The congenital imprinting disorder, Beckwith‐Wiedemann syndrome (BWS) is associated with variable clinical features including hemihypertrophy/lateralised overgrowth (LO) and embryonal tumour predisposition. BWS‐associated (epi)genetic alterations occur in a subset of patients with isolated LO (ILO), leading to the concept of BWS spectrum disorder (BWSp). We investigated the relationship between clinical features and molecular diagnostic results in a cohort with LO using the BWSp international consensus group (BWSICG) clinical scoring system. Clinical/molecular findings in 94 previously‐unreported patients with LO referred for BWSp molecular studies were reviewed retrospectively. The BWSICG score was assigned and diagnostic rate calculated. BWSp‐associated (epi)genetic alteration was identified in 15/94 (16%). The molecular diagnostic rate by MS‐MLPA (blood DNA) for BWS‐related molecular findings in patients with LO was positively correlated with the BWSICG score. 3/48 with ILO had a molecular alteration. No individuals with ILO had developed an embryonal tumour at last follow up. Among a cohort of individuals with LO referred for BWSp molecular testing, the BWSICG score correlated with diagnostic yield. The embryonal tumour risk in children with ILO and negative molecular testing appeared very low, however longer‐ and more complete follow up is required to better define tumour risks in this group.