Jennifer M. Bain

Constitutional deletions of chromosome 1q42 region are rare. The phenotype spectrum associated with this copy number change is variable, including developmental delay, intellectual disability, seizures, and dysmorphology. This study describes a patient with developmental delays and brain abnormalities. G-banded karyotype, FISH, SNP oligonucleotide microarray analysis (SOMA), and whole exome sequencing analysis were performed. Postnatal reanalysis of prenatal SOMA and follow-up parental testing revealed a paternally inherited 63 kb deletion at 1q42.11 in the patient. We characterized the clinical features of this patient, providing insight into the clinical phenotype associated with deletions of the 1q42.11 sub-band. Our study provides new evidence supporting the potential functional importance of the FBXO28 3′ UTR region and the hypothesis that FBXO28 is a critical gene in the pathogenesis of chromosome 1q41q42 microdeletion syndrome. It also highlights the different goals and reporting criteria between prenatal and postnatal microarray tests.

Rett Syndrome (RTT) is a neurodevelopmental disorder with a prevalence of 1:10,000 to 15,000 females worldwide. Classic Rett Syndrome presents in early childhood with a period of developmental regression, loss of purposeful hand skills along with hand stereotypies, gait abnormalities, and loss of acquired speech. Atypical RTT is diagnosed when a child shows some but not all the phenotypes of classic RTT, along with additional supporting criteria. Over 95% of classic RTT cases are attributed to pathogenic variants in Methyl-CpG Binding Protein 2 (MECP2), though additional genes have been implicated in other RTT cases, particularly those with the atypical RTT clinical picture. Other genetic etiologies have emerged with similar clinical characteristics to RTT Syndrome. Our team has characterized HNRNPH2-related neurodevelopmental disorder (HNRNPH2-RNDD) in 33 individuals associated with de novo pathogenic missense variants in the X-linked HNRNPH2 gene, characterized by developmental delay, intellectual disability, seizures, autistic-like features, and motor abnormalities. We sought to further characterize RTT clinical features in this group of individuals by using caregiver report. Twenty-six caregivers completed electronic surveys, with only 3 individuals having previously received an atypical RTT diagnosis, and no individuals with a typical RTT diagnosis. Caregivers reported a high number of behaviors and/or phenotypes consistent with RTT, including the major criteria of the syndrome, such as regression of developmental skills and abnormal gait. Based on the survey results, 12 individuals could meet the diagnostic clinical criteria for atypical RTT Syndrome. In summary, individuals with HNRNPH2-RNDD exhibit clinical characteristics that overlap with those of RTT, and therefore, HNRNPH2-RNDD, should be considered on the differential diagnosis list with this clinical picture.