Clinical Description
SETD1B-related neurodevelopmental disorder (SETD1B-NDD) is characterized by developmental delay (mainly affecting speech and language), intellectual disability, seizures, autism spectrum disorder or autism-like behaviors, and additional behavioral concerns including sleep disturbances. To date, 38 individuals have been identified with a pathogenic variant in SETD1B [Roston et al 2021, Weerts et al 2021, Álvarez-Mora et al 2022, Weng et al 2022]. The following description of the phenotypic features associated with SETD1B-NDD is based on these reports.
Global developmental delay. Speech delay and/or language disorders have been reported in most affected individuals. The range of speech impairment varied from isolated delays to more severe impairments. Of individuals for whom age at first word was reported, 14 of 30 spoke their first word after age two years [Roston et al 2021, Weerts et al 2021]. Out of a cohort of 36 individuals with SETD1B-NDD, three individuals were nonverbal at ages 2.5, 3, and 3.5 years [Weerts et al 2021]. Only two individuals were reported not to have language delay, and they were very young (10 and 12 months) at the time of assessment [Weerts et al 2021].
Delay in gross motor skills is frequent. When reported specifically, age at first walking ranged from 12 months to 4.5 years. One individual was reported as having normal motor development at age seven years [Hiraide et al 2019]. Detailed reports of fine motor milestones in individuals with SETD1B-NDD have yet to be published.
Developmental regression was observed in six of 38 individuals with SETD1B-NDD, and regression did not always coincide with seizure onset. Regression primarily affected speech; detailed descriptions of motor regression have not been published [Roston et al 2021, Weerts et al 2021, Álvarez-Mora et al 2022, Weng et al 2022].
The two individuals with reported normal development were evaluated at ages one and two years, and additional information for these individuals is not available.
Intellectual disability (ID) appears to be typically mild to moderate: 13 individuals with mild ID and ten individuals with moderate ID were reported. One individual was reported to have severe ID [Weerts et al 2021] and another individual was reported to have profound ID [Hiraide et al 2018].
Note: Patients reported as “intellectually disabled” at age younger than three years are included in global developmental delay.
Seizures. Affected individuals typically presented with seizures by age five years, although seizure onset at older ages was reported in six individuals [Roston et al 2021, Weerts et al 2021]. Two individuals with SETD1B-NDD presented with seizures at age six months or younger [Weerts et al 2021].
Seizure types were heterogeneous, and often included multiple seizure types or evolving seizure patterns. Seizure types included absence (18 individuals), myoclonic (13 individuals), generalized tonic-clonic (12 individuals), focal (4 individuals), and atonic (2 individuals). Of note, at least four individuals demonstrated eyelid myoclonia [Roston et al 2021, Weerts et al 2021].
Seizures occurred daily in most individuals and were reported to worsen with age. Seizures were intractable in at least four individuals [Roston et al 2021, Weerts et al 2021]. However, some individuals reported improvement with anti-seizure medication. No consistently effective anti-seizure treatment was identified.
Feeding difficulties have been reported in a small proportion of individuals.
Other neurologic findings
Microcephaly, with a head circumference of 2 SD below the mean, was identified in one adult with
SETD1B-NDD [
Weerts et al 2021].
Autism spectrum disorder and autistic features. The majority of reported individuals were either diagnosed with autism spectrum disorder (22/37) or had autistic features without a formal diagnosis (4 */37) [Roston et al 2021, Weerts et al 2021, Weng et al 2022].
* Includes patients reported as “autistic” at age younger than three years
Other behavioral concerns. Approximately half of reported individuals had other behavioral concerns including hyperactivity (10 individuals), aggression (9), anxiety (6), and sleep disturbance (6). A further three individuals demonstrated obsessive-compulsive behavior [Roston et al 2021, Weerts et al 2021, Weng et al 2022]. Behavioral issues have been more common in affected males.
Brain MRI abnormalities included nonspecific white matter hyperintensities, abnormalities of the corpus callosum, cystic encephalomalacia with ventriculomegaly, bilateral abnormal signals in multiple lobes, extensive abnormal gyral sulcation, delayed myelination and heterotopic grey matter, and periventricular leukomalacia. Of note, several individuals with abnormal brain MRI findings had an additional serious medical condition (e.g., periventricular leukomalacia in an individual with hypoplastic left heart) [Roston et al 2021, Weerts et al 2021, Weng et al 2022].
Nonspecific facial features. Many individuals with SETD1B-NDD were reported to have unusual craniofacial features, but without a clear recognizable pattern. Ear anomalies were common (e.g., overfolded helices, differences of ear lobe morphology, ear pits, ear tags). Several individuals had a high anterior hairline, frontal bossing, or anterior hairline recession [Roston et al 2021, Weerts et al 2021, Weng et al 2022]. Thickened facial features (e.g., full cheeks, thick lips, broad or bulbous nasal tip, wide nasal root) were frequently reported; it is unknown if coarse facial features were secondary to anti-convulsant therapy.
Ophthalmologic features. Strabismus has been reported infrequently; astigmatism, amblyopia, and myopia have also been reported [Weerts et al 2021].
Other. Each reported in one individual:
Dysplastic kidneys requiring transplant, an anteriorly placed anus, clubfeet, tethered cord, and contractures [
Weerts et al 2021]