Traits

Traits linked to SOS1

SOS Ras/Rac guanine nucleotide exchange factor 1

The Human Phenotype Ontology links 98 traits to SOS1, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of head or neck

Trait	How often it is seen
Depressed nasal bridge	Always
Eye folds	Always
Gingival fibromatosis	Always
Sparse eyebrow	Always
Cystic hygroma	Very often (80–99%)
Downward slanting of the opening between the eyelids	Very often (80–99%)
Full lips	Very often (80–99%)
Full lower lip	Very often (80–99%)
Gum enlargement	Very often (80–99%)
High forehead	Very often (80–99%)
High palate	Very often (80–99%)
Little lower jaw	Very often (80–99%)
Midface retrusion	Very often (80–99%)
Short neck	Very often (80–99%)
Thickened skin folds of neck	Very often (80–99%)
Triangular face	Very often (80–99%)
Webbed neck	Very often (80–99%)
Wide mouth	Very often (80–99%)
Big calvaria	Often (30–79%)
Low hairline at back of neck	Often (30–79%)
Bad bite	Not recorded
High frontal hairline	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal cardiovascular system morphology	Very often (80–99%)
Abnormal EKG	Very often (80–99%)
Narrowing of lung artery	Very often (80–99%)
Abnormal heart rate	Often (30–79%)
Abnormal pulmonary valve morphology	Often (30–79%)
Abnormality of the lymphatic system	Often (30–79%)
Abnormality of the spleen	Often (30–79%)
Narrowing of pulmonic valve	Often (30–79%)
An opening in the wall separating the top two chambers of the heart	Sometimes (5–29%)
Enlarged and thickened heart muscle	Sometimes (5–29%)
Hole in heart wall separating two lower heart chambers	Sometimes (5–29%)
Narrowing of aorta	Sometimes (5–29%)
Patent ductus arteriosus	Rarely (1–4%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Abnormality of the sternum	Always
Delayed bone maturation	Always
Funnel chest	Always
Scoliosis	Always
Double-Jointed	Very often (80–99%)
Muscle weakness	Very often (80–99%)
Pigeon chest	Very often (80–99%)
Wide rib cage	Very often (80–99%)
Low muscle tone	Often (30–79%)
Osteopenia	Sometimes (5–29%)
Pectus excavatum of inferior sternum	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Prolonged partial thromboplastin time	Always
Reduced factor VIII activity	Always
Reduced factor XI activity	Always
Abnormal platelet function	Often (30–79%)
Abnormality of coagulation	Often (30–79%)
Bleeding tendency	Often (30–79%)
Bruising susceptibility	Sometimes (5–29%)
Juvenile myelomonocytic leukemia	Sometimes (5–29%)
Low platelet count	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Blue eyes	Always
Drooping of both upper eyelids	Always
Drooping upper eyelid	Always
Wide-set eyes	Always
Bulging eye	Very often (80–99%)
Cross-eyed	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Curly hair	Very often (80–99%)
Abnormal fingerprints	Often (30–79%)
Abnormal hair quantity	Often (30–79%)
Chicken skin	Often (30–79%)
Coarse hair	Often (30–79%)
Beauty mark	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Ears rotated toward back of head	Always
Low-set ears	Always
Thickened helices	Always
Aplasia of the semicircular canal	Sometimes (5–29%)
Sensorineural hearing impairment	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Abnormality of the reproductive system	Often (30–79%)
Undescended testes	Often (30–79%)
Dilatation of the renal pelvis	Sometimes (5–29%)
Double ureter	Sometimes (5–29%)
Hydronephrosis	Sometimes (5–29%)

Abnormality of the nervous system

Trait	How often it is seen
Abnormal speech pattern	Very often (80–99%)
Difficulty articulating speech	Very often (80–99%)
Neurodevelopmental delay	Often (30–79%)
Intellectual disability	Sometimes (5–29%)
Specific learning disability	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Curvature of little finger	Sometimes (5–29%)
Fused forearm bones	Sometimes (5–29%)
Short fingers or toes	Sometimes (5–29%)
Outward turned elbows	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Absent/small abdominal wall muscles	Very often (80–99%)
Enlarged liver	Often (30–79%)
Feeding difficulties in infancy	Often (30–79%)

Growth abnormality

Trait	How often it is seen
Short stature	Very often (80–99%)
Birth weight > 90th percentile	Often (30–79%)
Growth delay as children	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Hypogonadotropic hypogonadism	Very often (80–99%)
Delayed start of first period	Sometimes (5–29%)

Abnormality of prenatal development or birth

Trait	How often it is seen
High levels of amniotic fluid	Always

Abnormality of the breast

Trait	How often it is seen
Wide-spaced nipples	Always

Laboratory abnormality

Trait	How often it is seen
Swelling caused by excess lymph fluid under skin	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 SOS1 and how often each is seen. Find out more at hpo.jax.org.

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