Traits

Traits linked to TBCD

tubulin folding cofactor D

The Human Phenotype Ontology links 84 traits to TBCD, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Delayed speech and language development	Always
Global developmental delay	Always
Intellectual disability	Always
Brisk reflexes	Very often (80–99%)
Decrease in size of the outer layer of the brain due to loss of brain cells	Very often (80–99%)
Epilepsy	Very often (80–99%)
Underdevelopment of part of brain called corpus callosum	Very often (80–99%)
Absent speech development	Often (30–79%)
Ataxia	Often (30–79%)
Cerebral hypomyelination	Often (30–79%)
Degeneration of cerebellum	Often (30–79%)
Generalized tonic seizure	Often (30–79%)
Grand mal seizures	Often (30–79%)
Inability to walk	Often (30–79%)
IQ less than 20	Often (30–79%)
Loss of developmental milestones	Often (30–79%)
Paralysis of all four limbs	Often (30–79%)
Poor speech	Often (30–79%)
Absent reflexes	Sometimes (5–29%)
Atrophy/Degeneration affecting the brainstem	Sometimes (5–29%)
Cataplexy	Sometimes (5–29%)
CNS hypomyelination	Sometimes (5–29%)
Epileptic spasm	Sometimes (5–29%)
IQ between 34 and 49	Sometimes (5–29%)
Muscle twitch	Sometimes (5–29%)
Ventriculomegaly	Sometimes (5–29%)
Dystonia	Rarely (1–4%)
Febrile seizure (within the age range of 3 months to 6 years)	Rarely (1–4%)
Motor axonal neuropathy	Rarely (1–4%)
Repetitive movements	Rarely (1–4%)
Diffuse cerebral atrophy	Not recorded
Encephalopathy	Not recorded
Gliosis	Not recorded
Loss of brain cells	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Development of small head that was not present at birth	Always
Abnormally small head	Often (30–79%)
Widely spaced teeth	Often (30–79%)
Asymmetry of the posterior head	Sometimes (5–29%)
Frontal bossing	Sometimes (5–29%)
Little lower jaw	Sometimes (5–29%)
Low hanging columella	Sometimes (5–29%)
Monobrow	Sometimes (5–29%)
Narrow forehead	Sometimes (5–29%)
Small head present at birth	Sometimes (5–29%)
Sparse eyebrow	Sometimes (5–29%)
Tongue twitching	Sometimes (5–29%)
Upward slanting of the opening between the eyelids	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Lower limb spasticity	Always
Muscle weakness	Always
Involuntary muscle stiffness, contraction, or spasm	Very often (80–99%)
Muscle degeneration	Very often (80–99%)
Scoliosis	Very often (80–99%)
Uncontrollable movement in upper arms	Very often (80–99%)
Decreased muscle tone in infant	Often (30–79%)
Low muscle tone	Often (30–79%)
Progressive spasticity	Often (30–79%)
Arthrogryposis multiplex congenita	Sometimes (5–29%)
Recurrent long bone fractures	Sometimes (5–29%)
Funnel chest	Rarely (1–4%)
Pigeon chest	Rarely (1–4%)

Abnormality of the eye

Trait	How often it is seen
Absent smooth pursuit	Always
Optic atrophy	Often (30–79%)
Cross-eyed	Sometimes (5–29%)
Deeply set eye	Sometimes (5–29%)
Involuntary, rapid, rhythmic eye movements	Sometimes (5–29%)
Wide-set eyes	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Constipation	Often (30–79%)
Feeding difficulties	Often (30–79%)
Chronic constipation	Sometimes (5–29%)
Loss of bowel control	Sometimes (5–29%)
Poor swallowing	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Retractile testis	Often (30–79%)
Loss of bladder control	Sometimes (5–29%)
Lack of bladder control due to nervous system injury	Rarely (1–4%)

Abnormality of the respiratory system

Trait	How often it is seen
Respiratory failure	Often (30–79%)
Respiratory function loss	Often (30–79%)
Respiratory failure requiring assisted ventilation	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Dislocated hip since birth	Rarely (1–4%)

Abnormality of prenatal development or birth

Trait	How often it is seen
High levels of amniotic fluid	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Large ears	Rarely (1–4%)

Abnormality of the immune system

Trait	How often it is seen
Recurrent pneumonia	Rarely (1–4%)

Abnormality of the integument

Trait	How often it is seen
Excessive hairiness	Rarely (1–4%)

Growth abnormality

Trait	How often it is seen
Growth delay	Very often (80–99%)

Laboratory abnormality

Trait	How often it is seen
Elevated blood creatine phosphokinase	Often (30–79%)

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

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