Expanded phenotypic spectrum of neurodevelopmental and neurodegenerative disorder Bryant-Li-Bhoj syndrome with 38 additional individuals

Bryant-Li-Bhoj syndrome (BLBS), which became OMIM-classified in 2022 (OMIM: 619720, 619721), is caused by germline variants in the two genes that encode histone H3.3 (H3-3A/H3F3A and H3-3B/H3F3B) [1-4]. This syndrome is characterized by developmental delay/intellectual disability, craniofacial anomalies, hyper/hypotonia, and abnormal neuroimaging [1, 5]. BLBS was initially categorized as a progressive neurodegenerative syndrome caused by de novo heterozygous variants in either H3-3A or H3-3B [1-4]. Here, we analyze the data of the 58 previously published individuals along 38 unpublished, unrelated individuals. In this larger cohort of 96 people, we identify causative missense, synonymous, and stop-loss variants. We also expand upon the phenotypic characterization by elaborating on the neurodevelopmental component of BLBS. Notably, phenotypic heterogeneity was present even amongst individuals harboring the same variant. To explore the complex phenotypic variation in this expanded cohort, the relationships between syndromic phenotypes with three variables of interest were interrogated: sex, gene containing the causative variant, and variant location in the H3.3 protein. While specific genotype-phenotype correlations have not been conclusively delineated, the results presented here suggest that the location of the variants within the H3.3 protein and the affected gene (H3-3A or H3-3B) contribute more to the severity of distinct phenotypes than sex. Since these variables do not account for all BLBS phenotypic variability, these findings suggest that additional factors may play a role in modifying the phenotypes of affected individuals. Histones are poised at the interface of genetics and epigenetics, highlighting the potential role for gene-environment interactions and the importance of future research.

Lessons from two series by physicians and caregivers' self-reported data in DDX3X-related disorders

INTRODUCTION AND METHODS

We report two series of individuals with DDX3X variations, one (48 individuals) from physicians and one (44 individuals) from caregivers.

RESULTS

These two series include several symptoms in common, with fairly similar distribution, which suggests that caregivers' data are close to physicians' data. For example, both series identified early childhood symptoms that were not previously described: feeding difficulties, mean walking age, and age at first words.

DISCUSSION

Each of the two datasets provides complementary knowledge. We confirmed that symptoms are similar to those in the literature and provides more details on feeding difficulties. Caregivers considered that the symptom attention-deficit/hyperactivity disorder were most worrisome. Both series also reported sleep disturbance. Recently, anxiety has been reported in individuals with DDX3X variants. We strongly suggest that attention-deficit/hyperactivity disorder, anxiety, and sleep disorders need to be treated.

[Neurofibromatosis von Recklinghausen type 1 (NF1) - clinical picture and molecular-genetics diagnostic]

Neurofibromatosis von Recklinghausen type 1 (NF1) is a multisystem, autosomal dominant hereditary neurocutaneous disease characterized by skin, central and peripheral nervous system , eyes , bone, endocrine, gastrointestinal and blood vessel wall involvement. It has an estimated frequency of 1 in 3000. Neurofibromatosis type 1 is caused by mutations in the large NF1 gene located on chromosome 17q11.2, encoding the cytoplasmic protein neurofibromin. It is expressed in multiple cell types but is highly expressed in Schwann cells, oligodendrocytes, neurons, astrocytes and leukocytes. Neurofibromin is known to act as a tumor suppressor via Ras-GTPase activation, which causes down-regulation of cellular signaling via the Ras/mitogen-activated protein kinase (MAPK) pathway. Failure of this function is associated with a tendency to form tumors which are histologically hamartomas as well as benign tumors. Tumors of the central nervous system include low-grade gliomas (pilocytic astrocytomas grade I), especially optic pathway gliomas. They are often clinically asymptomatic. Other intracranial tumors are in the brain stem and also elsewhere in the brain and spinal cord. Hydrocephalus may be a complication of NF1 gliomas or due to stenosis of the distal part of the aqueduct Silvii. Cutaneous and subcutaneous neurofibromas or plexiform neurofibromas are localized in the peripheral nervous system. Plexiform neurofibromas have a significant lifetime risk of malignancy. The clinical diagnosis of NF1 is defined by diagnostic criteria. The NF1 diagnosis is satisfied when at least two of the seven conditions are met. The method of direct DNA analysis of large NF1 gene (61 exons) is available. The results of studies of genotype - phenotype established few correlations. But predicting the disease by finding mutations is not currently possible. NF1 exhibits a wide range of variability of expression and complete penetrance, even within the same family. About half of cases are new mutations. The treatment of patients with neurofibromatosis is symptomatic. Central nervous system symptomatic low-grade gliomas are most often treated with chemotherapy. For plexiform neurofibromas surgical removal is currently the only treatment option.