Clinical Description
The cardinal features of Tatton-Brown-Rahman syndrome (TBRS) are overgrowth and mild-to-severe intellectual disability. Other common features include joint hypermobility, obesity / increased weight, hypotonia, behavioral/psychiatric problems, kyphoscoliosis, and seizures. To date, more than 90 individuals with a pathogenic variant in DNMT3A have been reported [Tatton-Brown et al 2014, Tlemsani et al 2016, Kosaki et al 2017, Lemire et al 2017, Shen et al 2017, Xin et al 2017, Tatton-Brown et al 2018, Sweeney et al 2019, Balci et al 2020, Hage et al 2020, Tenorio et al 2020, Yokoi et al 2020]. The following description of the phenotypic features associated with this condition is based on these reports and the authors' personal communications with the families.
Table 2.
Select Features of Tatton-Brown-Rahman Syndrome
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Feature | % of Persons w/Feature | Comment |
---|
Intellectual disability | 100% | Most often in mild-to-moderate range |
Overgrowth 1 | >80% |
|
Joint hypermobility | ~75% | |
Overweight 2 | ~65% | |
Hypotonia | ~55% | |
Behavioral/psychiatric issues | ~50% | Most commonly autism spectrum disorder |
Kyphoscoliosis | ~30% | |
Seizures | ~20% | |
Cryptorchidism | ~20% of males | |
Cardiovascular disease | ~10% | Most commonly congenital heart disease, although aortic root dilatation also observed |
Ventriculomegaly | <10% | |
Chiari malformation | <10% | |
Malignant tumors | ~5% | Most commonly acute myeloid leukemia 3 |
SD = standard deviation(s)
- 1.
Defined as length/height and/or head circumference ≥2 SD above the mean for age and sex
- 2.
Defined as weight ≥2 SD above the mean for age and sex
- 3.
This figure is an estimate based on cases reported to date; the precise risk remains unknown.
Growth. Overgrowth is present in more than 80% of affected individuals. However, clinical variability is seen among affected individuals and the absence of overgrowth does not preclude a diagnosis of TBRS.
Tall stature (height ≥2 standard deviations [SD] above the mean for age and sex) is present in about 70% of individuals. Height ranges from 0.3 SD below to 6 SD above the mean.
Macrocephaly (head circumference ≥2 SD above the mean for age and sex) is present in around 50% of affected individuals. Head circumference ranges from 1.2 SD below to 8.0 SD above the mean.
About 65% of affected individuals are overweight or obese (weight ≥2 SD above the mean for age and sex). Weight ranges from 1.1 SD below to 4.5 SD above the mean.
There is relatively little information about birth measurements, although overgrowth typically is present from early childhood. In those for whom measurements were available, mean birth weight was 1.3 SD above the mean (range: 1.1 SD below to 4.0 SD above mean), mean birth head circumference was 2.3 SD above the mean (range: 0.6 to 6.5 SD above mean), and mean birth length was 1.6 SD above the mean (range: 0.0 to 4.4 SD above mean) [Tatton-Brown et al 2018].
Developmental delay (DD) and intellectual disability (ID). All affected individuals reported to date have some degree of developmental delay and/or intellectual disability, ranging from mild to severe. While the specific severity is not reported for all known individuals, most of those who are described in detail (n=83) had intellectual disability in the mild-to-moderate range.
Mild ID (23/83, 28%). Children attend mainstream school and need some extra help – for example, a statement of educational needs (see
Management) – but would be expected to live independently as adults and may have their own family.
Moderate ID (48/83, 58%). Children develop speech and may be able to attend mainstream school with a high level of support, but more likely will attend a school or be in a program for individuals with special educational needs. While unlikely to live completely independently as adults, they may live in sheltered accommodation or with some additional support.
Severe ID (12/83, 14%). Individuals require special education during schooling and are likely to require considerable support in adulthood.
A subsequent publication reported more detailed cognitive and behavioral profiles of a smaller cohort (n=18, age 7-33 years) [Lane et al 2020]. The mean General Conceptual Ability score was 53 (range: 39-76). Nonverbal and spatial reasoning were more significantly impaired than verbal reasoning.
Behavior problems. The behavior problems seen in individuals with TBRS are most commonly associated with autism spectrum disorder.
In a series of 18 individuals with a confirmed molecular diagnosis, autistic traits were present in the majority, and eight (44%) fulfilled the ADOS-2 criteria for a formal diagnosis of autism [
Lane et al 2020].
The prevalence of autistic traits was lower in older individuals, suggesting that symptoms may improve with age, but this is based on cross-sectional assessment of a relatively small cohort rather than long-term observation.
Other behavior problems reported in a smaller proportion of affected individuals include [Tatton-Brown et al 2018, Tenorio et al 2020]:
Anxiety
Aggression
Psychotic disorders
Bipolar disorder
Obsessive behaviors
Compulsive eating
Musculoskeletal features. Generalized joint hypermobility is a common feature of TBRS. It can be associated with musculoskeletal pain and joint instability; joint dislocations are rare. Kyphoscoliosis is present in about 30% of affected individuals [Tatton-Brown et al 2018]. Widely spaced toes are a commonly reported feature, although the exact prevalence is unknown [Tatton-Brown et al 2018].
Hypotonia is present in a majority of individuals with TBRS [Tatton-Brown et al 2018] and may require physical therapy.
Epilepsy. Seizures are present in around 20% of people with TBRS [Tatton-Brown et al 2018]. Both febrile and afebrile seizures have been reported. There is limited information regarding the specific types of seizures, age of seizure onset, or whether specific anti-seizure medications are more effective than others in individuals with TBRS.
Neuroimaging. No specific or consistent imaging abnormalities are known to be characteristic of TBRS. Individual abnormalities detected on brain MRI have included ventriculomegaly and Chiari malformation [Kosaki et al 2017, Tatton-Brown et al 2018].
Genitourinary abnormalities. Cryptorchidism is present in about 20% of males with TBRS [Tatton-Brown et al 2018]. Other genitourinary abnormalities reported in a few individuals with TBRS include vesicoureteral reflux and hypospadias [Tatton-Brown et al 2018, Tenorio et al 2020].
Malignant tumors. There is evidence that the spectrum of germline DNMT3A pathogenic variants found in individuals with TBRS is similar to that found in sporadic, nonsyndromic malignancies [Shen et al 2017]. However, data are insufficient to determine the precise risk of malignancy to a given individual with TBRS. To date, hematologic malignancies have been reported in eight individuals with TBRS, suggesting a risk on the order of about 4% [Hollink et al 2017, Ferris et al 2022] (see Genotype-Phenotype Correlations and Cancer and Benign Tumors).
The most common malignancy is acute myeloid leukemia (AML; 4/8 individuals); cases of lymphoid malignancy and myelodysplastic syndrome have also been reported.
The median age at diagnosis is 9.6 years (range: age 2.5-12 years), with the cases of AML diagnosed between ages nine and 20 years.
Limited information exists regarding lifetime cancer risk in individuals with TBRS, as the majority of individuals identified to date who have developed cancer are children or young adults.
Single case reports of a specific cancer in an individual with TBRS have been published; however, in the absence of further known cases, it is not clear whether these tumors are specifically associated with TBRS or are rare co-occurrences. The tumors are as follows:
Ganglioneuroblastoma and T-cell lymphoblastic lymphoma [
Balci et al 2020]; this individual also had a truncating pathogenic variant in
CLTC.
Facial features. While the facial gestalt of TBRS may not be as clinically recognizable as other overgrowth disorders (e.g., Sotos syndrome), common facial features are shared by a significant proportion of affected individuals. The facial features are most characteristic in adolescence and less specific in early childhood or adulthood. They include the following [Tatton-Brown et al 2018]:
A round face with coarse features (describing some loss of definition of the nose, lips, mouth, and chin because of rounded and heavy features)
Thick horizontal low-set (i.e., closer than anticipated to the orbit) eyebrows
Narrow (as measured vertically) palpebral fissures
Prominent upper central incisors
Other associated features. The following are less common features seen in affected individuals, including features reported in only one affected individual each. It remains to be confirmed whether the feature is specifically associated with TBRS or is a rare co-occurrence.
Cardiovascular disease. Aortic root dilatation has been reported in several individuals with TBRS [
Tatton-Brown et al 2018,
Tenorio et al 2020,
Cecchi et al 2022]. Aortic dissection and sudden cardiac death have not been reported, and it remains to be established whether aortic dilatation is static or progressive. Congenital heart defects (atrial septal defect, ventricular septal defect, persistent ductus arteriosus) are also commonly reported by families (although not yet published as a frequent association in the literature). A longitudinal study is under way to quantify the incidence. Less common cardiovascular features, reported in one affected individual each, include the following [
Kosaki et al 2017,
Tatton-Brown et al 2018,
Cecchi et al 2022]:
Mitral valve prolapse
Dilated cardiomyopathy
Arrhythmia
Congenital diaphragmatic hernia has been described in one affected individual [
Balci et al 2020].
Autonomic dysfunction including postural orthostatic hypotension and episodic vasomotor instability in the extremities have been reported in four affected individuals [
Balci et al 2020].
Prognosis. Data on whether TBRS alters life span are limited. Since many adults with disabilities have not undergone advanced genetic testing and mutation of DNMT3A was first recognized to be associated with a clinical phenotype in 2014 [Tatton-Brown et al 2014], it is likely that adults with this condition are underrecognized and underreported.