Traits

Traits linked to ALG2

ALG2 alpha-1,3/1,6-mannosyltransferase

The Human Phenotype Ontology links 96 traits to ALG2, by body system: features seen in people with one of the gene's rare conditions.

ALG2

Abnormality of the nervous system

Trait	How often it is seen
Delayed CNS myelination	Always
Epileptic spasm	Always
Hypsarrhythmia	Always
Infantile spasms	Always
Intellectual disability, severe	Always
Motor delay	Always
Severe global developmental delay	Always
Abnormal peripheral nervous system synaptic transmission	Often (30–79%)
Abnormality of the nervous system	Often (30–79%)
Absent reflexes	Often (30–79%)
Delayed speech and language development	Often (30–79%)
Dystonia	Often (30–79%)
Epilepsy	Often (30–79%)
Favorable response of weakness to acetylcholine esterase inhibitors	Often (30–79%)
Focal T2 hyperintense basal ganglia lesion	Often (30–79%)
Global developmental delay	Often (30–79%)
Intellectual disability	Often (30–79%)
Poor eye contact	Often (30–79%)
Thin corpus callosum	Often (30–79%)
Ventriculomegaly	Often (30–79%)
Abnormal basal ganglia MRI signal intensity	Sometimes (5–29%)
Abnormal gait	Sometimes (5–29%)
Cerebral hypomyelination	Sometimes (5–29%)
Hyperintensity of cerebral white matter on MRI	Sometimes (5–29%)
Lateral ventricle dilatation	Sometimes (5–29%)
Underdevelopment of part of brain called corpus callosum	Sometimes (5–29%)
Waddling gait	Sometimes (5–29%)
Widened subarachnoid space	Sometimes (5–29%)
Increased reflexes	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
EMG: decremental response of compound muscle action potential to repetitive nerve stimulation	Always
Fatigable weakness	Always
Increased variability in muscle fiber diameter	Always
Centrally nucleated skeletal muscle fibers	Often (30–79%)
Distal joint hypermobility	Often (30–79%)
Double-Jointed	Often (30–79%)
Generalized decreased muscle tone	Often (30–79%)
Increased jitter at single fiber EMG	Often (30–79%)
Low muscle tone	Often (30–79%)
Muscle tissue disease	Often (30–79%)
Proximal neurogenic muscle weakness	Often (30–79%)
Type 1 muscle fiber predominance	Often (30–79%)
Difficulty running	Sometimes (5–29%)
Difficulty walking up stairs	Sometimes (5–29%)
Excessive inward curvature of lower spine	Sometimes (5–29%)
Flexed joint that cannot be straightened	Sometimes (5–29%)
Frequent falls	Sometimes (5–29%)
Gowers sign	Sometimes (5–29%)
Muscle spasm	Sometimes (5–29%)
Poor head control	Sometimes (5–29%)
Prominent swayback	Sometimes (5–29%)
Ragged-red muscle fibers	Sometimes (5–29%)
Scoliosis	Sometimes (5–29%)
Tired easily	Sometimes (5–29%)
Weakness of outermost muscles	Rarely (1–4%)

Abnormality of head or neck

Trait	How often it is seen
Weakness of facial musculature	Very often (80–99%)
Abnormal facial shape	Often (30–79%)
Abnormally small head	Often (30–79%)
Downward slanting of the opening between the eyelids	Often (30–79%)
Eye folds	Often (30–79%)
Flat face	Often (30–79%)
High palate	Often (30–79%)
Upward slanting of the opening between the eyelids	Often (30–79%)
Wide nasal bridge	Often (30–79%)
Bell's palsy	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Cat eye	Always
Involuntary, rapid, rhythmic eye movements	Always
Visual impairment	Always
Clouding of the lens of the eye	Often (30–79%)
Esodeviation	Often (30–79%)
Inward turning cross eyed	Often (30–79%)
Drooping upper eyelid	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Limb-girdle muscle weakness	Always
Dropped arches	Often (30–79%)
Inability to straighten knee	Often (30–79%)
Generalized weakness of limb muscles	Sometimes (5–29%)
Winged shoulder blade	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Prolonged partial thromboplastin time	Always
Reduced factor XI activity	Always
Abnormality of coagulation	Often (30–79%)
Iron deficiency anemia	Often (30–79%)

Abnormality of the digestive system

Trait	How often it is seen
Enlarged liver	Always
Acid reflux	Often (30–79%)
Diarrhea	Often (30–79%)
Nasogastric tube feeding	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
Type I transferrin isoform profile	Always
Abnormal circulating enzyme concentration or activity	Very often (80–99%)
Mildly elevated creatine kinase	Often (30–79%)
Elevated blood creatine phosphokinase	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Low-set ears	Often (30–79%)
Sensorineural hearing impairment	Often (30–79%)

Growth abnormality

Trait	How often it is seen
Decreased body weight	Often (30–79%)
Short stature	Often (30–79%)

Abnormal cellular phenotype

Trait	How often it is seen
Muscle fiber tubular inclusions	Often (30–79%)

Abnormality of the breast

Trait	How often it is seen
Inverted nipples	Often (30–79%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Dilation of Virchow-Robin spaces	Often (30–79%)

Abnormality of the endocrine system

Trait	How often it is seen
Underactive thyroid	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 ALG2 and how often each is seen. Find out more at hpo.jax.org.

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