Traits

Traits linked to SIM1

SIM bHLH transcription factor 1

The Human Phenotype Ontology links 98 traits to SIM1, 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
Abnormal autonomic nervous system physiology	Very often (80–99%)
Cognitive impairment	Very often (80–99%)
Delayed speech and language development	Very often (80–99%)
Global developmental delay	Very often (80–99%)
Increased appetite	Very often (80–99%)
Motor delay	Very often (80–99%)
Abnormal temper tantrums	Often (30–79%)
Attention deficit	Often (30–79%)
Autism spectrum disorder	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Brain imaging abnormality	Often (30–79%)
Diminished deep tendon reflex	Often (30–79%)
Intellectual disability	Often (30–79%)
Memory impairment	Often (30–79%)
Neurodevelopmental delay	Often (30–79%)
Skin-picking	Often (30–79%)
Specific learning disability	Often (30–79%)
Ventriculomegaly	Often (30–79%)
Abnormal rapid eye movement sleep	Sometimes (5–29%)
Central sleep apnea	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Impaired temperature sensation	Sometimes (5–29%)
Incoordination	Sometimes (5–29%)
Lethargy	Sometimes (5–29%)
Obstructive sleep apnea	Sometimes (5–29%)
Psychosis	Sometimes (5–29%)
Wide based walk	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Abnormal facial shape	Very often (80–99%)
Almond shaped eyes	Often (30–79%)
Big calvaria	Often (30–79%)
Full cheeks	Often (30–79%)
Narrow forehead	Often (30–79%)
Upward slanting of the opening between the eyelids	Often (30–79%)
Broad forehead	Sometimes (5–29%)
Bulbous nose	Sometimes (5–29%)
Decreased salivary flow	Sometimes (5–29%)
Depressed nasal bridge	Sometimes (5–29%)
Downturned corners of mouth	Sometimes (5–29%)
Little lower jaw	Sometimes (5–29%)
Narrow nasal bridge	Sometimes (5–29%)
Nasal tip, upturned	Sometimes (5–29%)
Receding chin	Sometimes (5–29%)
Thick eyebrow	Sometimes (5–29%)
Thin red part of the upper lip	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Decreased activity of gonads	Very often (80–99%)
Absence of pubertal development	Often (30–79%)
Hypogonadotropic hypogonadism	Often (30–79%)
Hypothalamic luteinizing hormone-releasing hormone deficiency	Often (30–79%)
Small pituitary gland	Often (30–79%)
Central hypothyroidism	Sometimes (5–29%)
Early onset of puberty	Sometimes (5–29%)
Premature adrenarche	Sometimes (5–29%)
Premature pubic hair growth	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Infertility	Very often (80–99%)
Undescended testes	Very often (80–99%)
Decreased testicular size	Often (30–79%)
Primary amenorrhea	Often (30–79%)
Small clitoris	Often (30–79%)
Smaller than typical growth of scrotum	Often (30–79%)
Underdeveloped inner lips	Often (30–79%)
Underdevelopment of external reproductive organs	Often (30–79%)
Short penis	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Decreased muscle tone in infant	Very often (80–99%)
Low muscle tone, in neonatal onset	Often (30–79%)
Scoliosis	Often (30–79%)
Abnormal formation of the hip	Sometimes (5–29%)
Abnormality of the chest	Sometimes (5–29%)
Osteopenia	Sometimes (5–29%)
Osteoporosis	Sometimes (5–29%)
Low muscle tone	Not recorded

Laboratory abnormality

Trait	How often it is seen
Hyperinsulinemia	Very often (80–99%)
Vitamin B1 deficiency	Very often (80–99%)
Glucose intolerance	Sometimes (5–29%)
Noninsulin-dependent diabetes	Sometimes (5–29%)
Increased resting energy expenditure	Not recorded

Abnormality of limbs

Trait	How often it is seen
Short foot	Often (30–79%)
Small hand	Often (30–79%)
Long foot	Sometimes (5–29%)
Tapered finger	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Obesity	Very often (80–99%)
Abdominal obesity	Often (30–79%)
Faltering weight	Often (30–79%)
Short stature	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Nasogastric tube feeding	Often (30–79%)
Poor suck	Often (30–79%)
Feeding difficulties	Not recorded

Abnormality of the ear

Trait	How often it is seen
Abnormal ear morphology	Sometimes (5–29%)
Low-set ears	Sometimes (5–29%)
Small ears	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Cross-eyed	Often (30–79%)
Abnormality of the eye	Sometimes (5–29%)
Chorioretinal hypopigmentation	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Low blood pressure	Very often (80–99%)
Postural hypotension with compensatory tachycardia	Very often (80–99%)

Abnormality of the integument

Trait	How often it is seen
Loss of hair color	Sometimes (5–29%)
Patchy lightened skin	Sometimes (5–29%)

Abnormality of the immune system

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

Abnormality of the voice

Trait	How often it is seen
Weak cry	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 SIM1 and how often each is seen. Find out more at hpo.jax.org.

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