The Tatton-Brown-Rahman Syndrome: A clinical study of 55 individuals with de novo constitutive DNMT3A variants

Tatton-Brown-Rahman syndrome (TBRS; OMIM 615879), also known as the DNMT3A-overgrowth syndrome, is an overgrowth intellectual disability syndrome first described in 2014 with a report of 13 individuals with constitutive heterozygous DNMT3A variants. Here we have undertaken a detailed clinical study of 55 individuals with de novo DNMT3A variants, including the 13 previously reported individuals. An intellectual disability and overgrowth were reported in >80% of individuals with TBRS and were designated major clinical associations. Additional frequent clinical associations (reported in 20-80% individuals) included an evolving facial appearance with low-set, heavy, horizontal eyebrows and prominent upper central incisors; joint hypermobility (74%); obesity (weight ³2SD, 67%); hypotonia (54%); behavioural/psychiatric issues (most frequently autistic spectrum disorder, 51%); kyphoscoliosis (33%) and afebrile seizures (22%). One individual was diagnosed with acute myeloid leukaemia in teenage years. Based upon the results from this study, we present our current management for individuals with TBRS

In this report we have undertaken a detailed clinical evaluation of 55 individuals with de novo DNMT3A variants, including the 13 individuals we first reported in 2014. We have expanded and clarified the TBRS phenotype, delineating major and frequent clinical associations, which has informed our management of individuals with this new OGID syndrome.

Methods
The study was approved by the London Multicentre Research Ethics Committee (MREC MREC/01/2/44). Patients were identified through Clinical Genetics Services worldwide and written informed consent was obtained from all participating individuals and/or parents. Photographs, with accompanying written informed consent to publish, were requested from all participants and received from the families of 41 individuals. Detailed phenotype data were collected through a standardized clinical proforma, a DNMT3A specific clinical proforma and clinical review by one of the authors. Growth parameter standard deviations were calculated with reference to UK90 growth data 10 .
The degree of intellectual disability was defined in relation to educational support as a child and living impairment as an adult: an individual with a mild intellectual disability typically had delayed milestones but would attend a mainstream school with some support and live independently, with support, as an adult; an individual with a moderate intellectual disability typically required high level support in a mainstream school or special educational needs schooling and would live with support as an adult; an individual with a severe intellectual disability typically required special educational needs schooling, had limited speech, and would not live independently as an adult.
55 individuals were included with a range of de novo heterozygous DNMT3A variants: missense variants (36 individuals with 30 different variants); stop gain variants (six individuals); frameshift variants (six individuals); whole gene deletions (four individuals including identical twins (COG1961 and COG2006)); in-frame deletions (two individuals) and a splice site variant (one individual, Figure 1, Table 1). Computational tools predicted all 30 missense variants to be deleterious (Mutation Taster2 and SIFT (version 6.2.1), Supplementary Table 1) and the splice site variant was predicted to disrupt normal splicing. Importantly, some of the variants are common in the general population due to
Postnatal overgrowth (defined as height and/or head circumference at least two standard deviations above the mean (≥2SD) 2,13 , was reported in 83% (44/53) individuals. Obesity, with a weight ≥2SD, was reported in 67% (34/51). The range of individual postnatal heights, head circumferences and weights is shown in Table 1 and Figure 3. The mean birth weight was 1.3SD with a range from -1.1 to 4.0 SD. We had limited data for birth head circumference and birth length, but their mean was 2.3SD and 1.6SD, respectively.
There were some shared, but subtle, facial characteristics often only becoming apparent in early adolescence (Figure 4a and b). These included low-set, horizontal thick eyebrows; narrow palpebral fissures; coarse features and a round face. The two upper central incisors were also frequently enlarged and prominent.
Clinical features reported in at least two but fewer than 20% individuals included cryptorchidism (six individuals); ventriculomegaly (four individuals) and Chiari malformation (three individuals). In addition, a range of cardiac anomalies (including atrial septal defect, mitral/tricuspid valve incompetence, patent ductus arteriosus, aortic root enlargement and atrio-ventricular re-entry tachycardia) were reported in nine individuals. However, of note, two individuals with cardiac anomalies (patent ductus arteriosus, COG1961 and COG2006) were identical twins with DNMT3A whole gene deletions encompassing >40 genes. The patent ductus arteriosus in these individuals may, therefore, be attributable to twinning, alternative genes in the deleted region or the combined effect of a number of deleted genes.
Acute myeloid leukaemia (AML), AML-FAB (French-American-British classification) type M4, was diagnosed in one individual Full clinical details from the 55 individuals are provided in Table 1.

Discussion
We have evaluated clinical data from 55 individuals with de novo constitutive DNMT3A variants to define the phenotype of TBRS. An intellectual disability (most frequently in the moderate range) and overgrowth (defined as height and/or head circumference ≥2SD above the mean) were reported in ≥80% of individuals and have been designated major clinical associations. Frequent clinical associations, reported in 20-80% of individuals with constitutive DNMT3A variants, included joint hypermobility, obesity, hypotonia, behavioural/psychiatric issues (most frequently autistic spectrum disorder), kyphoscoliosis and afebrile seizures. In addition, many individuals had a characteristic facial appearance although this may only be recognizable in adolescence.
TBRS overlaps clinically with other OGID syndromes including Sotos syndrome (OMIM 117550), Weaver syndrome (OMIM 277590), Malan syndrome (OMIM 614753) and the OGID syndrome due to CHD8 gene variants 2 . However, TBRS is more frequently associated with increased weight than the other OGID syndromes and may be distinguishable through recognition of the associated facial features, and absence of the facial gestalt of other OGID syndromes.
Somatic DNMT3A variants are known to drive the development of adult AML and myelodysplastic syndrome and over half of the DNMT3A somatic variants target a single residue, the p.Arg882 residue 14-17 . AML, diagnosed in childhood, has now been identified in two individuals with (likely) constitutive DNMT3A variants from a total of 77 (1/55 individuals in the current study and 1/22 previously reported individuals) 7 . One of these individuals had a   The majority of individuals with TBRS are healthy and do not require intensive clinical follow up. However, our practice is to inform families and paediatricians of the possible TBRS complications of behavioural/psychiatric issues, kyphoscoliosis and afebrile seizures to introduce a low threshold for their investigation and/or management. In addition, we undertake a baseline echocardiogram at initial diagnosis to investigate cardiac anomalies detectable on ultrasound scan and frequently refer patients to physiotherapy to evaluate the degree of hypotonia and/or joint hypermobility and to determine whether targeted exercises may be beneficial. Finally, in the absence of evidence-based surveillance protocols for haematological malignancies, we advise clinical vigilance for symptoms possibly related to a haematological malignancy such as easy bruising, recurrent bleeding from gums or nosebleeds, persistent tiredness and recurrent infections.

Ethics and consent
The study was approved by the London Multicentre Research Ethics Committee (MREC MREC/01/2/44).
Written informed consent was obtained from participants and/or parents for participation in the study (n=55) and publication of photographs of participants shown in Figure 4 (n=41).

Data availability
All data underlying the results are available as part of the article and no additional source data are required.

If applicable, is the statistical analysis and its interpretation appropriate? Not applicable
Are all the source data underlying the results available to ensure full reproducibility? Yes

Are the conclusions drawn adequately supported by the results? Yes
We confirm that we have read this submission and believe that we have an appropriate level