Traits

Traits linked to PPP1R21

protein phosphatase 1 regulatory subunit 21

The Human Phenotype Ontology links 60 traits to PPP1R21, 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
Broad columella	Always
Low hanging columella	Always
Nasal tip, upturned	Always
Short nose	Always
Coarse facial features	Often (30–79%)
Corners of eye widely separated	Often (30–79%)
Eye folds	Often (30–79%)
Flat back of skull	Often (30–79%)
Full lips	Often (30–79%)
High forehead	Often (30–79%)
High palate	Often (30–79%)
Long philtrum	Often (30–79%)
Narrow forehead	Often (30–79%)
Narrow nasal bridge	Often (30–79%)
Thick eyebrow	Often (30–79%)
Upward slanting of the opening between the eyelids	Often (30–79%)
Wide nasal bridge	Often (30–79%)
Asymmetry of the posterior head	Sometimes (5–29%)
Delayed cranial suture closure	Sometimes (5–29%)
Flattened bony protrusion above eyes	Sometimes (5–29%)
Short chin	Sometimes (5–29%)
Tented mouth	Sometimes (5–29%)

Abnormality of the nervous system

Trait	How often it is seen
Cerebellar vermis hypoplasia	Always
Decreased reflex response	Always
Global developmental delay	Always
Severe global developmental delay	Always
Ventriculomegaly	Always
Attention deficit	Often (30–79%)
Cavum septum pellucidum	Often (30–79%)
Difficulty articulating speech	Often (30–79%)
Extra-axial cerebrospinal fluid accumulation	Often (30–79%)
Inability to coordinate movements when walking	Often (30–79%)
Inability to walk	Often (30–79%)
Underdevelopment of part of brain called corpus callosum	Often (30–79%)
Absent reflexes	Sometimes (5–29%)
Myoclonic seizure	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Blue outer white part of eyeball	Often (30–79%)
Close sighted	Often (30–79%)
Inward turning cross eyed	Often (30–79%)
Optic atrophy	Often (30–79%)
Rotary nystagmus	Often (30–79%)
Wide-set eyes	Often (30–79%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Always
Delayed bone maturation	Often (30–79%)
Flexed joint that cannot be straightened	Often (30–79%)
Pigeon chest	Often (30–79%)
Scoliosis	Often (30–79%)

Abnormality of the digestive system

Trait	How often it is seen
Chronic constipation	Often (30–79%)
Feeding difficulties	Often (30–79%)
Enlarged liver	Sometimes (5–29%)
Poor suck	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Overlapping fingers	Sometimes (5–29%)
Overlapping toe	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
An opening in the wall separating the top two chambers of the heart	Often (30–79%)
Enlarged and thickened heart muscle	Sometimes (5–29%)

Abnormality of the ear

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

Abnormality of the immune system

Trait	How often it is seen
Recurrent respiratory infections	Often (30–79%)

Abnormality of the integument

Trait	How often it is seen
Excessive face hair	Often (30–79%)

Abnormality of the respiratory system

Trait	How often it is seen
Breathing difficulties	Often (30–79%)

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 PPP1R21 and how often each is seen. Find out more at hpo.jax.org.

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