Schaaf-Yang syndrome

Other Names: Prader-Willi syndrome due to a point mutation; PWS due to a point mutation; MAGEL2-related Prader-Willi-like syndrome; MAGEL2-related PWLS; Prader-Willi syndrome due to point mutation; PWS due to point mutation; Prader-Willi-like syndrome

Schaaf-Yang syndrome is a genetic condition that affects many parts of the body and is similar to Prader-Willi syndrome.

Epidemiology

According to the information provided by Schaaf, there are currently about more than 100 cases worldwide with Schaaf-Yang syndrome.

Schaaf suggests that the low incidence of cases could be due to:

• The syndrome was recently described so it is widely unknown in the medical community.
• Currently the syndrome is diagnosed by complete exome sequencing ; a technology which is not available in many places and is often not covered by insurers worldwide.
• The gene is very difficult to sequence, since it is very rich in CG.
• It is common that de novo inheritance is not taken into account in exome sequencing, because it is not on the list of identification genes. This would lead to the failure of the detection of cases whose etiology is de novo, because this type of mutations of the MAGEL2 gene that can be inherited by an unaffected parent would be filtering.

Cause

Schaaf-Yang syndrome is caused by a mutation in the MAGEL2 gene on chromosome 15. This syndrome is related to Prader-Willi syndrome because if MAGEL2 and several additional genes on chromosome 15 are missing or inactivated, then a person will develop Prader-Willi syndrome.

Signs and symptoms

Infants with this syndrome can have low muscle tone (hypotonia), feeding difficulties, developmental delay, intellectual disability, and autism spectrum disorder. They also typically have joint contractures, affecting the finger joints and sometimes the knees and elbows. This syndrome does not usually cause the high appetite seen in people with Prader-Willi syndrome.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Abnormal facial shape(Unusual facial appearance)
• Cryptorchidism(Undescended testes)
• Flexion contracture(Flexed joint that cannot be straightened)
• Infantile muscular hypotonia(Decreased muscle tone in infant)
• Infertility
• Motor delay
• Neonatal hypotonia(Low muscle tone, in neonatal onset)
• Poor suck(Poor sucking)

30%-79% of people have these symptoms

• Abdominal obesity(Central obesity)
• Abnormal temper tantrums
• Absence of pubertal development
• Autistic behavior
• Brain imaging abnormality
• Chronic constipation(Infrequent bowel movements)
• Clitoral hypoplasia(Small clitoris)
• Cognitive impairment(Abnormality of cognition)
• Decreased fetal movement(Less than 10 fetal movements in 12 hours)
• Decreased testicular size(Small testes)
• Delayed speech and language development(Deficiency of speech development)
• Failure to thrive(Faltering weight)
• Gastroesophageal reflux(Acid reflux)
• Hypogonadism(Decreased activity of gonads)
• Hypoplastic labia minora(Underdeveloped inner lips)
• Hypothalamic luteinizing hormone-releasing hormone deficiency
• Intellectual disability, borderline(Mental retardation, borderline)
• Intellectual disability, mild(Mental retardation, borderline-mild)
• Kyphosis(Hunched back)
• Nasogastric tube feeding
• Polyphagia(Voracious appetite)
• Primary amenorrhea
• Reduced tendon reflexes
• Scoliosis
• Scrotal hypoplasia(Smaller than typical growth of scrotum)
• Short foot(Short feet)
• Short stature(Decreased body height)
• Skin-picking
• Small hand(Disproportionately small hands)
• Small pituitary gland
• Specific learning disability
• Temperature instability
• Ventriculomegaly
• Weak cry

Diagnosis

Diagnosis is made by complete sequencing of the exome or the MAGEL2 gene.

Treatment

According to Schaaf, the key to treatment is early intervention and aimed primarily at treating symptoms, most children require extensive medical care in the first years of life, such as feeding tubes, gastrostomy , respiratory support and tracheostomies . The physical therapy helps reduce contractures which generally are not treated with medication, because the cause is the lack of movement rather than a rheumatologic process .

In Schaaf's words, “Research is currently under way on whether growth hormone treatment would make sense. Recombinant growth hormone has been a staple in the treatment of PWS for many years; This not only helps us with longitudinal growth, but also (and perhaps more importantly) helps us with muscular strength and endurance, in addition, this hormone changes the body composition from adipose tissue to lean muscle mass.

NIH genetic and rare disease info

• NIH info on Schaaf-Yang syndrome

Schaaf-Yang syndrome is a rare disease.

Schaaf-Yang syndrome Resources
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