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What is Weaver syndrome and explain in detail?
Weaver syndrome is a 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. 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. Forty-eight cases had been documented and confirmed as of December 2013, and its prevalence is estimated to be similar to that of Sotos syndrome, around 1 in 15,000. It was first described by American physician David Weaver in 1974.

Signs and symptoms
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:

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. They also have some neurological abnormalities such as speech delay, epilepsy, intellectual disability, hypotonia or hypertonia, and behavioral problems.

Cause
The cause for Weaver syndrome was identified in 2011 as autosomal dominant mutations in the EZH2 gene on chromosome 7q36. 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.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.

Diagnosis
Differential diagnosis
Weaver syndrome and Sotos syndrome are often mistaken for one another due to their significant phenotypic overlap and similarities. Clinical features shared by both syndromes include overgrowth in early development, advanced bone age, developmental delay, and prominent macrocephaly