Traits

Traits linked to B9D2

B9 domain containing 2

The Human Phenotype Ontology links 94 traits to B9D2, by body system: features seen in people with one of the gene's rare conditions.

B9D2

Abnormality of head or neck

Trait	How often it is seen
Bifid uvula	Always
Brain tissue sticks out through back of skull	Always
Dandy-Walker malformation	Always
Abnormally small head	Very often (80–99%)
Encephalocele	Very often (80–99%)
Cleft palate	Often (30–79%)
Decreased width of the skull	Often (30–79%)
Flat nose	Often (30–79%)
Full cheeks	Often (30–79%)
Little lower jaw	Often (30–79%)
Long face	Often (30–79%)
Sloping forehead	Often (30–79%)
Aplasia/Hypoplasia of the tongue	Sometimes (5–29%)
Cleft of the mouth	Sometimes (5–29%)
Grooved tongue	Sometimes (5–29%)
Highly arched eyebrow	Sometimes (5–29%)
Nasal tip, upturned	Sometimes (5–29%)
Prominent nasal bridge	Sometimes (5–29%)
Eye folds	Not recorded
Frontal bossing	Not recorded
Narrow eyelid opening	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Dilated fourth ventricle	Always
Small cerebellum	Always
Ataxia	Very often (80–99%)
Cerebellar vermis hypoplasia	Very often (80–99%)
Global developmental delay	Very often (80–99%)
Intellectual disability	Very often (80–99%)
Abnormal gait	Often (30–79%)
Anencephaly	Often (30–79%)
Lobar holoprosencephaly	Often (30–79%)
Abnormality of neuronal migration	Sometimes (5–29%)
Aplasia/Hypoplasia of the corpus callosum	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
More grooves in brain	Sometimes (5–29%)
Too much cerebrospinal fluid in the brain	Sometimes (5–29%)
Tremor	Sometimes (5–29%)
Molar tooth sign on MRI	Not recorded

Abnormality of the eye

Trait	How often it is seen
Oculomotor apraxia	Very often (80–99%)
Abnormal chorioretinal morphology	Often (30–79%)
Abnormally small eyeball	Often (30–79%)
Absent/small iris	Often (30–79%)
Clouding of the lens of the eye	Often (30–79%)
Cornea of eye less than 10mm in diameter	Often (30–79%)
Hardening of skin and connective tissue	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Optic atrophy	Often (30–79%)
Wide-set eyes	Often (30–79%)
Absence of eyeballs	Sometimes (5–29%)
Cat eye	Sometimes (5–29%)
Cross-eyed	Sometimes (5–29%)
Drooping upper eyelid	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Cystic kidney disease	Always
Hypospadias	Always
Short penis	Always
Multicystic kidney dysplasia	Very often (80–99%)
Ambiguous external genitalia	Often (30–79%)
Undescended testes	Often (30–79%)
Double ureter	Sometimes (5–29%)
Male pseudohermaphroditism	Sometimes (5–29%)
True hermaphroditism	Sometimes (5–29%)
Urethral atresia	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Extra little finger	Always
Extra toe attached near the little toe	Always
Postaxial polydactyly	Always
Ulnar deviation of the hand	Always
Talipes	Often (30–79%)
Bowing of the long bones	Sometimes (5–29%)
Duplication of bones of the toes	Sometimes (5–29%)
Extra finger	Sometimes (5–29%)
Extra thumb	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Malformation of the hepatic ductal plate	Always
Excessive buildup of connective tissue and scarring of liver at birth	Very often (80–99%)
Feeding difficulties in infancy	Often (30–79%)
Cystic liver disease	Sometimes (5–29%)
Enlarged colon lacking nerve cells	Sometimes (5–29%)
Pancreatic cysts	Sometimes (5–29%)
Pancreatic fibrosis	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal cardiovascular system morphology	Sometimes (5–29%)
Absent spleen	Sometimes (5–29%)
Accessory spleen	Sometimes (5–29%)
All organs on wrong side of body	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Permanent flexion of the finger or toe	Always
Low muscle tone	Very often (80–99%)
Abnormal vertebral body morphology	Sometimes (5–29%)
Scoliosis	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Ears rotated toward back of head	Often (30–79%)
Low-set ears	Sometimes (5–29%)
Abnormally shaped ears	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Abnormal pattern of respiration	Very often (80–99%)
Apnea	Very often (80–99%)
Episodic tachypnea	Very often (80–99%)

Abnormality of prenatal development or birth

Trait	How often it is seen
Low levels of amniotic fluid	Often (30–79%)

Abnormality of the endocrine system

Trait	How often it is seen
Abnormality of the hypothalamus-pituitary axis	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Spinal dimple	Not recorded

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 B9D2 and how often each is seen. Find out more at hpo.jax.org.

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