Table 2.

Select Features of Schaaf-Yang Syndrome

Feature% of Persons
w/Feature		Comment
DD/ID 100%
Muscular hypotonia 100%
Infantile hypotonia 95%-100%
Feeding difficulties in infancy 95%-100%
Flexion contractures >85%
Autistic behavior 75%-85%
Dysmorphic features 75%-85%Incl pointed chin, frontal bossing, low-set ears
Ocular anomalies 75%-85%Incl esotropia, myopia, strabismus
Behavioral abnormalities 70%-80%Incl impulsivity, compulsivity, stubbornness, manipulative behavior, skin picking / automutilation
Sleep apnea 70%-80%
Respiratory distress 65%-75%
Small hands 65%-75%Other hand anomalies: tapered fingers, clinodactyly, camptodactyly, brachydactyly, adducted thumbs
Chronic constipation 65%-75%
Temperature instability 60%-70%
Short feet 55%-65%
↓ fetal movement55%-65%
GERD 50%-60%
Scoliosis 50%-60%
Short stature 50%-60%
Polyphagia/Obesity 30%-40%Onset in late childhood/adolescence. Frequency of this feature ↑ w/age.
Seizures 30%-40%
Kyphosis 25%-35%
Hypogonadism 15%-65%15%-25% of females & 55%-65% of males, based on appearance of external genitalia

DD = developmental delay; GERD = gastroesophageal reflux; ID = intellectual disability

From: Schaaf-Yang Syndrome

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