Traits

Traits linked to YY1

YY1 transcription factor

The Human Phenotype Ontology links 119 traits to YY1, by body system: features seen in people with one of the gene's rare conditions.

YY1

Abnormality of the nervous system

Trait	How often it is seen
Delayed speech and language development	Always
Intellectual disability	Always
Motor delay	Always
Epilepsy	Very often (80–99%)
Global developmental delay	Very often (80–99%)
Transient global amnesia	Very often (80–99%)
Tremor	Very often (80–99%)
Behavioral abnormality	Often (30–79%)
Delayed ability to walk	Often (30–79%)
Disturbances of consciousness	Often (30–79%)
Fluctuations in consciousness	Often (30–79%)
Increased appetite	Often (30–79%)
Intellectual disability, mild	Often (30–79%)
IQ between 34 and 49	Often (30–79%)
Abnormal cerebral white matter morphology	Sometimes (5–29%)
Abnormal rapid eye movement sleep	Sometimes (5–29%)
Abnormality of mental function	Sometimes (5–29%)
Abnormality of pain sensation	Sometimes (5–29%)
Absent speech development	Sometimes (5–29%)
Agenesis of corpus callosum	Sometimes (5–29%)
Anxiety	Sometimes (5–29%)
Attention deficit	Sometimes (5–29%)
Autism	Sometimes (5–29%)
Autism spectrum disorder	Sometimes (5–29%)
Cancer of early nerve cells	Sometimes (5–29%)
Coma	Sometimes (5–29%)
Cortical dysplasia	Sometimes (5–29%)
Delayed CNS myelination	Sometimes (5–29%)
Delayed myelination	Sometimes (5–29%)
Difficulty sleeping	Sometimes (5–29%)
Difficulty staying or falling asleep	Sometimes (5–29%)
Dystonia	Sometimes (5–29%)
Gliosis	Sometimes (5–29%)
Intellectual disability, severe	Sometimes (5–29%)
Lateral ventricle dilatation	Sometimes (5–29%)
Lethargy	Sometimes (5–29%)
Pins and needles feeling	Sometimes (5–29%)
Severe global developmental delay	Sometimes (5–29%)
Toe walking	Sometimes (5–29%)
Underdevelopment of part of brain called corpus callosum	Sometimes (5–29%)
Ventriculomegaly	Sometimes (5–29%)
Waddling gait	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Broad forehead	Always
Abnormal facial shape	Very often (80–99%)
Bulbous nose	Very often (80–99%)
Full lower lip	Very often (80–99%)
Zygomatic flattening	Very often (80–99%)
Abnormality of the red part of the upper lip	Often (30–79%)
Broad nasal tip	Often (30–79%)
Downward slanting of the opening between the eyelids	Often (30–79%)
Facial asymmetry	Often (30–79%)
Fullness around the eyes	Often (30–79%)
Pointed chin	Often (30–79%)
Abnormal dentition	Sometimes (5–29%)
Corners of eye widely separated	Sometimes (5–29%)
Decreased facial muscle tone	Sometimes (5–29%)
Deformity of the skull	Sometimes (5–29%)
Epiblepharon	Sometimes (5–29%)
High palate	Sometimes (5–29%)
Little lower jaw	Sometimes (5–29%)
Long, narrow head	Sometimes (5–29%)
Narrowing of the tear duct	Sometimes (5–29%)
Pierre-Robin sequence	Sometimes (5–29%)
Sparse eyebrow	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Bunion	Sometimes (5–29%)
Dislocated kneecap	Sometimes (5–29%)
Gap between 1st and 2nd toes	Sometimes (5–29%)
Increased mobility in finger joint	Sometimes (5–29%)
Long fingers	Sometimes (5–29%)
Partial knee cap dislocation	Sometimes (5–29%)
Sydney crease	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Abnormality of the pancreatic islet cells	Very often (80–99%)
Feeding difficulties	Very often (80–99%)
Feeding difficulties in infancy	Often (30–79%)
Gastrostomy tube feeding in infancy	Often (30–79%)
Oral-pharyngeal dysphagia	Often (30–79%)
Zollinger-Ellison syndrome	Often (30–79%)
Birth defect in which part of esophagus did not develop	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Pituitary prolactin cell adenoma	Often (30–79%)
Primary hyperparathyroidism	Often (30–79%)
Decreased response to growth hormone stimulation test	Sometimes (5–29%)
Neoplasm of the adrenal gland	Sometimes (5–29%)
Neuroendocrine neoplasm	Sometimes (5–29%)
Underactive thyroid	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
High blood insulin levels while fasting	Very often (80–99%)
Hyperinsulinemia	Very often (80–99%)
Hyperinsulinemic hypoglycemia	Very often (80–99%)
Nonketotic hypoglycemia	Very often (80–99%)
Recurrent low blood sugar levels	Very often (80–99%)
Low blood sugar after a meal	Often (30–79%)

Abnormality of the eye

Trait	How often it is seen
Cross-eyed	Often (30–79%)
Abnormality of vision	Sometimes (5–29%)
Astigmatism	Sometimes (5–29%)
Drooping upper eyelid	Sometimes (5–29%)
Farsightedness	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Palpitations	Very often (80–99%)
Aortopulmonary collateral arteries	Sometimes (5–29%)
Ebstein anomaly of the tricuspid valve	Sometimes (5–29%)
Patent foramen ovale	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Ears rotated toward back of head	Often (30–79%)
Simple ear	Often (30–79%)
Hearing abnormality	Sometimes (5–29%)
Low-set ears	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Generalized muscle weakness	Often (30–79%)
Low muscle tone	Often (30–79%)
Distal arthrogryposis	Sometimes (5–29%)
Distal lower limb amyotrophy	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Hydronephrosis	Sometimes (5–29%)
Undescended testes	Sometimes (5–29%)
Ureteropelvic junction obstruction	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Excessive sweating	Very often (80–99%)
Frontal upsweep of hair	Sometimes (5–29%)
Hyperelastic skin	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Increased body weight	Often (30–79%)
Prenatal growth deficiency	Often (30–79%)
Small for gestational age	Sometimes (5–29%)

Abnormality of the breast

Trait	How often it is seen
Underdeveloped breasts	Sometimes (5–29%)

Abnormality of the immune system

Trait	How often it is seen
Recurrent infections	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Fatigue	Sometimes (5–29%)

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to YY1 and how often each is seen. Find out more at hpo.jax.org.

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