Weaver syndrome | |
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Other names | Weaver–Smith syndrome |
Specialty | Medical genetics |
Weaver syndrome is an extremely rare autosomal dominant genetic disorder associated with rapid growth beginning in the prenatal period and continuing through the toddler and youth years. It is characterized by advanced osseous maturation and distinctive craniofacial, skeletal and neurological abnormalities. [1] It is similar to Sotos syndrome and is classified as an overgrowth syndrome.
Its genetic cause was identified in 2011 as mutations in the EZH2 gene. [2] Forty-eight cases had been documented and confirmed as of December 2013 [update] , [3] and its prevalence is estimated to be similar to that of Sotos syndrome, around 1 in 15,000. [4] It was first described by American physician David Weaver in 1974. [5]
Children with Weaver syndrome tend to look similar and have distinctive physical and craniofacial characteristics, which may include several, but not all, of the following features: [6]
Other features may include loose skin, thin deep-set nails, thin hair, short ribs, limited elbow and knee extension, camptodactyly, and a coarse, low-pitched voice. Delayed development of motor skills such as sitting, standing, and walking are commonly exhibited in early childhood. Patients with Weaver syndrome typically have mild intellectual disability with poor coordination and balance. [7] They also have some neurological abnormalities such as speech delay, epilepsy, intellectual disability, hypotonia or hypertonia, and behavioral problems.[ citation needed ]
The cause for Weaver syndrome was identified in 2011 as autosomal dominant mutations in the EZH2 gene on chromosome 7q36. [2] EZH2 (Enhancer of Zeste, Drosophila, homolog 2) is the second histone methyltransferase associated with human overgrowth. It encodes the catalytic component of the PRC2 protein complex (Polycomb Repressive Complex 2), which regulates chromatin structure and gene expression, and has been found to repress transcription. EZH2 also has critical roles in stem cell maintenance and cell lineage determination, such as osteogenesis, myogenesis, lymphopoiesis and hematopoiesis.
It can also be associated with mutations in the histone methyltransferase NSD1 gene on chromosome 5q35. The functions of NSD1 are not clearly known, but it is thought to act as a factor in influencing transcription, which contains domains involved in chromatin-mediated regulation during development. [8]
Most cases are found to be sporadic, with no family history of the syndrome, although there have been a few cases in families where autosomal dominant inheritance has been reported. [9]
Weaver syndrome and Sotos syndrome are often mistaken for one another due to their significant phenotypic overlap and similarities. [10] Clinical features shared by both syndromes include overgrowth in early development, advanced bone age, developmental delay, and prominent macrocephaly. [11] Mutations in the NSD1 gene may also be another cause for confusion. The NSD1 gene provides instructions for making a protein that is involved in normal growth and development. Deletions and mutations in the NSD1 gene is a common cause for patients with Sotos syndrome and in some cases for Weaver syndrome as well. [6]
Features distinguishing Weaver syndrome from Sotos syndrome include broad forehead and face, ocular hypertelorism, prominent wide philtrum, micrognathia, deep-set nails, retrognathia with a prominent chin crease, increased prenatal growth, and a carpal bone age that is greatly advanced compared to metacarpal and phalangeal bone age. [12]
There is no cure available for Weaver syndrome. However, with multidisciplinary management such as neurological, pediatric, orthopedic and psychomotor care and genetic counseling, symptoms can be managed. Surgery may be used to correct any skeletal issues. Physical and occupational therapy are considered an option to help with muscle tone. Also, speech therapy is often recommended for speech related problems.[ medical citation needed ]
With appropriate treatment and management, patients with Weaver syndrome appear to do well, both physically and intellectually, throughout their life and have a normal lifespan.[ medical citation needed ] Their adult height can reach 7–8 feet (213.36–243.84 cm). [13]
The incidence of Weaver syndrome is uncertain, as the causative mutation was only identified in 2011. As of December 2013 [update] , 48 cases of Weaver syndrome had been documented and confirmed. [3] [14] In 2012, the South West Thames Regional Genetic Service at St George's Hospital in London, based on their detection rate among a cohort of patients within their Childhood Overgrowth Study, estimated a prevalence rate similar to that of Sotos syndrome, around 1 in 15,000. [4]
The condition was first described by American physician David Weaver in 1974. [5]
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes, a white forelock or patches of light skin. These basic features constitute type 2 of the condition; in type 1, there is also a wider gap between the inner corners of the eyes called telecanthus, or dystopia canthorum. In type 3, which is rare, the arms and hands are also malformed, with permanent finger contractures or fused fingers, while in type 4, the person also has Hirschsprung's disease. There also exist at least two types that can result in central nervous system (CNS) symptoms such as developmental delay and muscle tone abnormalities.
Nonsyndromic deafness is hearing loss that is not associated with other signs and symptoms. In contrast, syndromic deafness involves hearing loss that occurs with abnormalities in other parts of the body. Nonsyndromic deafness constitutes 75% of all hearing loss cases, and an estimated 100 genes are thought to be linked to this condition. About 80% are linked to autosomal recessive inheritance, 15% to autosomal dominant inheritance, 1-3% through the X chromosome, and 0.5-1% are associated with mitochondrial inheritance.
Costello syndrome, also called faciocutaneoskeletal syndrome or FCS syndrome, is a rare genetic disorder that affects many parts of the body. It is characterized by delayed development and intellectual disabilities, distinctive facial features, unusually flexible joints, and loose folds of extra skin, especially on the hands and feet. Heart abnormalities are common, including a very fast heartbeat (tachycardia), structural heart defects, and overgrowth of the heart muscle. Infants with Costello syndrome may be large at birth, but grow more slowly than other children and have difficulty feeding. Later in life, people with this condition have relatively short stature and many have reduced levels of growth hormones. It is a RASopathy.
Simpson–Golabi–Behmel syndrome (SGBS) is a rare inherited congenital disorder that can cause craniofacial, skeletal, vascular, cardiac, and renal abnormalities. There is a high prevalence of cancer associated in those with SGBS which includes wilms tumors, neuroblastoma, tumors of the adrenal gland, liver, lungs and abdominal organs. The syndrome is inherited in an X-linked recessive manner. Females that possess one copy of the mutation are considered to be carriers of the syndrome but may still express varying degrees of the phenotype, suffering mild to severe malady. Males experience a higher likelihood of fetal death.
Hajdu–Cheney syndrome, also called acroosteolysis with osteoporosis and changes in skull and mandible, arthrodentoosteodysplasia and Cheney syndrome, is an extremely rare autosomal dominant congenital disorder of the connective tissue characterized by severe and excessive bone resorption leading to osteoporosis and a wide range of other possible symptoms. Mutations in the NOTCH2 gene, identified in 2011, cause HCS. HCS is so rare that only about 50 cases have been reported worldwide since the discovery of the syndrome in 1948
Acrocephalosyndactyly is a group of congenital conditions characterized by irregular features of the face and skull (craniosynostosis) and hands and feet (syndactyly). Craniosynostosis occurs when the cranial sutures, the fibrous tissue connecting the skull bones, fuse the cranial bones early in development. Cranial sutures allow the skull bones to continue growing until they fuse at age 24. Premature fusing of the cranial sutures can result in alterations to the skull shape and interfere with brain growth. Syndactyly occurs when digits of the hands or feet are fused together. When polydactyly is also present, the classification is acrocephalopolysyndactyly. Polydactyly occurs when the hands or feet possess additional digits. Acrocephalosyndactyly is usually diagnosed after birth, although prenatal diagnosis is sometimes possible if the genetic variation is present in family members, as the conditions are typically inherited in an autosomal dominant pattern Treatment often involves surgery in early childhood to correct for craniosynostosis and syndactyly.
Papillorenal syndrome is an autosomal dominant genetic disorder marked by underdevelopment (hypoplasia) of the kidney and colobomas of the optic nerve.
Laminopathies are a group of rare genetic disorders caused by mutations in genes encoding proteins of the nuclear lamina. They are included in the more generic term nuclear envelopathies that was coined in 2000 for diseases associated with defects of the nuclear envelope. Since the first reports of laminopathies in the late 1990s, increased research efforts have started to uncover the vital role of nuclear envelope proteins in cell and tissue integrity in animals.
NSD1 is a transcription coregulator protein that encodes Histone Methyltransferase and is associated with Sotos syndrome and Weaver syndrome.
Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase enzyme encoded by EZH2 gene, that participates in histone methylation and, ultimately, transcriptional repression. EZH2 catalyzes the addition of methyl groups to histone H3 at lysine 27, by using the cofactor S-adenosyl-L-methionine. Methylation activity of EZH2 facilitates heterochromatin formation thereby silences gene function. Remodeling of chromosomal heterochromatin by EZH2 is also required during cell mitosis.
Perlman syndrome (PS), also known as nephroblastomatosis-fetal ascites-macrosomia-Wilms tumor syndrome, is a rare overgrowth syndrome caused by autosomal recessive mutations in the DIS3L2 gene. PS is characterized by macrocephaly, neonatal macrosomia, nephromegaly, renal dysplasia, dysmorphic facial features, and increased risk for Wilms' tumor. The syndrome is associated with high neonatal mortality.
Sotos syndrome is a rare genetic disorder characterized by excessive physical growth during the first years of life. Excessive growth often starts in infancy and continues into the early teen years. The disorder may be accompanied by autism, mild intellectual disability, delayed motor, cognitive, and social development, hypotonia, and speech impairments. Children with Sotos syndrome tend to be large at birth and are often taller, heavier, and have relatively large skulls (macrocephaly) than is normal for their age. Signs of the disorder, which vary among individuals, include a disproportionately large skull with a slightly protrusive forehead, large hands and feet, large mandible, hypertelorism, and downslanting eyes. Clumsiness, an awkward gait, and unusual aggressiveness or irritability may also occur.
Nablus mask-like facial syndrome is a rare genetic condition. It is a microdeletion syndrome triggered by a deletion at chromosome 8 q22.1 that causes a mask-like facial appearance in those affected. This syndrome typically presents itself in infants, specifically newborns.
Hereditary gingival fibromatosis (HGF), also known as idiopathic gingival hyperplasia, is a rare condition of gingival overgrowth. HGF is characterized as a benign, slowly progressive, nonhemorrhagic, fibrous enlargement of keratinized gingiva. It can cover teeth in various degrees, and can lead to aesthetic disfigurement. Fibrous enlargement is most common in areas of maxillary and mandibular tissues of both arches in the mouth. Phenotype and genotype frequency of HGF is 1:175,000 where males and females are equally affected but the cause is not entirely known. It mainly exists as an isolated abnormality but can also be associated with a multi-system syndrome.
Andermann syndrome, also known as agenesis of corpus callosum with neuronopathy (ACCPN), Charlevoix disease and KCC3 axonopathy among other names, is a very rare neurodegenerative genetic disorder that damages the nerves used to control muscles and related to sensation and is often associated with agenesis of the corpus callosum.
Hypertension and brachydactyly syndrome (HTNB), also known as Bilginturan syndrome and brachydactyly type E among others, is a very rare genetic disorder.
Multiple congenital anomalies-hypotonia-seizures syndrome is a rare multi-systemic genetic disorder which is characterized by developmental delay, seizures, hypotonia and heart, urinary, and gastrointestinal abnormalities.
CAPOS syndrome is a rare genetic neurological disorder which is characterized by abnormalities of the feet, eyes and brain which affect their normal function. These symptoms occur episodically when a fever-related infection is present within the body. The name is an acronym for "cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss".
Tatton-Brown–Rahman syndrome (TBRS) is a rare overgrowth and intellectual disability syndrome caused by autosomal dominant mutations in the DNMT3A gene. The syndrome was first recognized in 2014 by Katrina Tatton-Brown, Nazneen Rahman, and collaborators.
Malan syndrome (MALNS) is a rare overgrowth syndrome caused by autosomal dominant mutations in the NFIX gene. The syndrome is characterized by overgrowth, craniofacial dysmorphia, intellectual disability, and behavioral issues. It was formerly diagnosed as Sotos syndrome 2.