Clinical Description
The phenotypic spectrum associated with germline EZH2 pathogenic variants is broad, with classic Weaver syndrome at one end of the spectrum and tall stature at the other. Although most individuals diagnosed with a heterozygous germline EZH2 pathogenic variant have been identified because of a clinical suspicion of Weaver syndrome, a minority have been identified through molecular genetic testing of family members of probands or individuals with overgrowth who did not have a clinical diagnosis of Weaver syndrome [Tatton-Brown et al 2011, Gibson et al 2012]. Thus, the extent of the phenotypic spectrum of heterozygous EZH2 pathogenic variants is not yet known. While data are still limited, clinical associations reported to date in 54 individuals with Weaver syndrome are summarized below [Tatton-Brown et al 2011, Gibson et al 2012, Al-Salem et al 2013, Tatton-Brown et al 2013, Usemann et al 2016, Suri & Dixit 2017, Lui et al 2018]. The denominators reflect the numbers of individuals for whom data are available.
Growth. From data available on 23 newborns, the mean birth length was 2.2 standard deviations above the mean (+2.2 SD) with a range of -0.5 SD to +4.9 SD; the mean birth weight of 45 newborns was +1.7 SD with a range of -1.6 SD to +4.6 SD [Tatton-Brown et al 2013].
Tall stature is a near-consistent finding: height in 47/52 individuals was at least two standard deviations above the mean (ages 1-70 years). Of note, three of the four individuals with a height less than +2 SD had been tall as young children. The mean postnatal height was +3.5 SD.
Of 45 individuals on whom information was available, 24 had a head circumference less than +2 SD and 21 had macrocephaly with a head circumference ranging up to +5.5 SD.
Cognitive features. Information on cognitive function was available for 50 individuals. Eight had normal intellect; 42 individuals had variable intellectual disability (ID) including the following:
Mild ID (24/50). Children attend mainstream school and need some extra help – e.g., a statement of educational needs – but would be expected to live independently as adults and would be likely to have their own family.
Moderate ID (14/50). Children develop speech and need a high level of support in mainstream education but more likely will attend a school for individuals with special educational needs. While unlikely to live independently as adults, they may live in sheltered accommodation or with some additional support.
Severe ID (2/50). Individuals require special education during schooling and are likely to require considerable support in adulthood.
Unclassified ID (2/50). Information provided is insufficient to make a determination.
Behavioral issues including autistic spectrum disorder, phobias, and anxiety have been anecdotally reported.
Neurologic. Ventriculomegaly, reported in six individuals, was generally associated with normal CSF pressure and did not require shunting [Tatton-Brown et al 2013]. Other brain MRI findings included neuronal migration defects (pachy/polymicrogyria; in 2 individuals), periventricular leukomalacia (2 individuals), and cerebellar abnormalities (2 individuals).
Intellectual disability in those with a brain MRI abnormality was:
Mild in six (ventriculomegaly [4], periventricular leukomalacia [1], and cerebellar hypoplasia [1]);
Moderate in three (periventricular leukomalacia with ventriculomegaly [1] and
isolated ventriculomegaly [2]);
Severe in an individual with polymicrogyria and pachygyria; in contrast, the individual with polymicrogyria reported by
Al-Salem et al [2013] had normal developmental milestones and body asymmetry (left side smaller than the right) with brisk reflexes and increased tone on the left.
Note: The degree of intellectual disability was not reported for one individual with ventriculomegaly.
Four individuals had afebrile seizures.
Skeletal features
Advanced bone age. Of 29 individuals evaluated, all had advanced bone age.
Scoliosis was reported in nine individuals and pectus abnormalities (excavatum or carinatum) in three. Scoliosis ranged from severe (early-childhood onset requiring surgical intervention) to mild (requiring monitoring but no therapeutic intervention).
Camptodactyly. Some affected individuals had camptodactyly of the fingers, some had camptodactyly of the toes, and some had camptodactyly of fingers and toes. On occasion the toe camptodactyly required surgical correction.
Adult boutonniere deformity. Several adults developed hyperextension of the distal interphalangeal joints and flexion of the proximal interphalangeal joints of the hands analogous to a mild boutonniere deformity ().
Talipes equinovarus. Six individuals had talipes equinovarus ranging from fixed and bilateral (requiring surgery) in two individuals to mild (unilateral that resolved with physiotherapy) in three.
Mild hyperextension of the distal interphalangeal joints and flexion of the proximal interphalangeal joints in a woman age 22 years with a heterozygous EZH2 pathogenic variant
Connective tissue
Ligamentous laxity. While ligamentous laxity with associated joint hypermobility and pes planus is common, it is not usually reported unless complicated by joint pain. Individuals with EZH2-related overgrowth are frequently reported to have poor coordination that may be (at least partially) attributable to lax ligaments.
Skin that was soft and doughy to the touch was seen in 19/37 affected children.
Umbilical hernia, seen in 21/44 children, was sufficiently large to require surgery in the neonatal period in eight.
Abnormal tone. In general, if present, abnormal tone (hypotonia, hypertonia, or mixed central hypotonia and peripheral hypertonia) resolved during childhood.
Hypotonia (predominantly central) was reported in 22/45 individuals.
Hypertonia (predominantly peripheral manifesting as stiffness in the limbs with brisk reflexes) was reported in 13/41.
Note: Five of the individuals presenting with peripheral hypertonia were also reported to have central hypotonia.
Poor feeding was reported in 10/28 neonates including one who required nasogastric tube feeding for two weeks. Although poor feeding may be attributable to neonatal hypotonia, this was only reported in three of the infants with poor feeding.
Hoarse, low-pitched cry was reported in 10/27 affected infants.
Tumors have been reported in four of 54 affected individuals [Tatton-Brown et al 2013, Usemann et al 2016].
One boy with a
c.2233G>A pathogenic variant developed a pre-T cell non-Hodgkins lymphoma at age 13 years. At age 25 years he remains well with no relapses or additional tumors.
One boy with a
c.2044G>A pathogenic variant was diagnosed at age 13 months with acute lymphoblastic leukemia and neuroblastoma, both of which responded to therapy; he is well at age seven years.
One girl with a
c.395C>T pathogenic variant was diagnosed with acute myeloid leukemia and secondary hemophagocytic lymphohistiocytosis at age 16 years.
Additional clinical features reported in a small number of individuals (and therefore, possibly not associated with the EZH2 pathogenic variant) are included for completeness:
Café au lait macules (in 2 individuals), hemangioma (in 4)
Hypermetropia (hyperopia) (3), myopia (1), strabismus (3)
Cryptorchidism (1), hydrocele (2), hypospadias (1)
Cleft palate (3)
Hearing loss (3) – conductive and sensorineural
Cardiac anomalies (4) including mitral valve prolapse (1), ventricular septal defect (2), and patent ductus arteriosus (1)
Gastroesophageal reflux (1), hiatal hernia (1)
Neonatal hypoglycemia (2)
Neonatal hypocalcemia (1)