Skip to content

Angelman syndrome





Population genetics
Genetic disorders
Down syndrome (Trisomy 21)
Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fragile X syndrome
Huntington disease
Myotonic dystrophy
Friedreich ataxia
Turner syndrome
Klinefelter syndrome
Prader-Willi syndrome
Angelman syndrome
Beckwith-Wiedemann syndrome
Cri du chat syndrome
Williams syndrome
Alagille syndrome (NORD)
Polycystic kidney disease
Familial adenomatous polyposis
Familial hypercholesterolemia
Hereditary spherocytosis
Huntington disease
Li-Fraumeni syndrome
Marfan syndrome
Multiple endocrine neoplasia
Myotonic dystrophy
Treacher Collins syndrome
Tuberous sclerosis
von Hippel-Lindau disease
Polycystic kidney disease
Cystic fibrosis
Friedreich ataxia
Gaucher disease (NORD)
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Krabbe disease
Niemann-Pick disease types A and B (NORD)
Niemann-Pick disease type C
Primary ciliary dyskinesia
Phenylketonuria (NORD)
Sickle cell disease (NORD)
Tay-Sachs disease (NORD)
Wilson disease
Fragile X syndrome
Alport syndrome
X-linked agammaglobulinemia
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Lesch-Nyhan syndrome
Muscular dystrophy
Ornithine transcarbamylase deficiency
Wiskott-Aldrich syndrome
Mitochondrial myopathy
Autosomal trisomies: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
Miscellaneous genetic disorders: Pathology review

Angelman syndrome


0 / 8 complete


0 / 2 complete
High Yield Notes
4 pages

Angelman syndrome

8 flashcards

USMLE® Step 1 style questions USMLE

2 questions

A 4-year-old girl with severe intellectual disability is brought to the physician for follow-up. The patient is nonverbal, and she did not begin walking until the age of two. Last year, she was initiated on valproate due to recurrent seizures. During the interview, the physician notices that the patient smiles constantly and laughs most of the time. She claps her hands and laughs hysterically without prompting. Family history is negative for neurological disorders. At the end of the interview, the mother asks the physician about the possibility of having additional children with the same condition. Which of the following is the most appropriate response by the physician?  

External References

Content Reviewers:

Rishi Desai, MD, MPH


Tanner Marshall, MS

Angelman syndrome is a genetic disorder that causes intellectual and developmental delay, seizures, frequent laughter, and ataxia, or poor control of voluntary movements.

Now, it happens when a gene on chromosome 15 called UBE3A is not expressed, or transcribed into messenger RNA.

UBE3A stands for ubiquitin-protein ligase E3A, and the protein it codes for is called E6AP or E6-associated protein.

The job of E6AP is to go around tagging, or attaching, a tiny protein called ubiquitin to other proteins, a process called ubiquitination.

Once that happens, the ubiquitinated protein is degraded by the proteasome, a part of the cell’s recycling machinery.

It’s kind of painting an orange U on a tree so that a lumberjack knows to chop it down.

So E6 associated protein has an important job, and it turns out that the region of chromosome 15 around UBE3A is imprinted, imprinting refers to gene expression that’s dependent on the parent of origin of a gene.

This means that either the maternally derived or paternally derived copy of the gene is silenced.

This differs from most genes in the genome, where both the maternal and paternal copies are expressed.

Normally, in the brain, only the maternally derived copy of UBE3A is expressed, while the paternal copy is silenced, unfortunately this process of imprinting leaves the maternal copy of UBE3A vulnerable.

So with the paternal copy of the gene imprinted, and epigenetically silenced, you’ve only got the maternal copy left.

So this means that if anything happens to the maternal copy, the result is Angelman syndrome.

There are a few different types of mutations that can cause Angelman syndrome.

The most common one is a deletion of a couple million base pairs of DNA on the maternal copy of chromosome 15 which includes UBE3A.

Sometimes the deletion overlaps a nearby gene called OCA2, which codes for a pigment that gives color to eye, hair, and skin.

As a result of this, these Angelman syndrome patients can have a light complexion.

A second way is a mutation within the maternal copy of UBE3A, making the protein ineffective.

A third way to get Angelman syndrome is when the entire maternal chromosome 15 is absent and instead there’s an extra copy of the paternal chromosome 15.

This scenario is called paternal uniparental disomy, which means that one parent – the father – contributed two of the same chromosome while the mother contributed none.


Angelman syndrome (AS) is a genetic neurodevelopmental disorder characterized by problems with motor skills, speech, developmental delay, and learning disabilities. People with AS typically have happy dispositions and frequently laugh or smile, even when they are not engaged in activities that would typically elicit such reactions.

Most individuals with AS do not develop fluent speech, have sleep disturbance, and usually have seizures. People with AS typically have a normal life expectancy and have the potential to improve on some self-help skills with proper supportive care.