Traits

Traits linked to PYGM

glycogen phosphorylase, muscle associated

The Human Phenotype Ontology links 30 traits to PYGM, by body system: features seen in people with one of the gene's rare conditions.

Laboratory abnormality

Trait	How often it is seen
Reduced muscle glycogen phosphorylase activity	Always
Elevated blood creatine phosphokinase	Very often (80–99%)
Glycogen accumulation in muscle fiber lysosomes	Very often (80–99%)
Highly elevated creatine kinase	Very often (80–99%)
Increased muscle glycogen content	Very often (80–99%)
Dark urine	Often (30–79%)
Exercise-induced myoglobinuria	Often (30–79%)
High blood uric acid level	Often (30–79%)
Myoglobinuria	Often (30–79%)
Recurrent myoglobinuria	Often (30–79%)
Failure to elevate lactate upon ischemic exercise test	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Breakdown of skeletal muscle	Often (30–79%)
Exercise-induced muscle cramps	Often (30–79%)
Exercise-induced muscle stiffness	Sometimes (5–29%)
Muscle degeneration	Sometimes (5–29%)
Muscle weakness	Sometimes (5–29%)
Progressive proximal muscle weakness	Sometimes (5–29%)
Exercise-induced rhabdomyolysis	Not recorded

Constitutional symptom

Trait	How often it is seen
Decreased ability to exercise	Very often (80–99%)
Exercise-induced muscle pain	Sometimes (5–29%)
Fatigue	Sometimes (5–29%)
Postexertional symptom exacerbation	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Failure to elevate ammonia on ischemic exercise	Always
Elevated heart rate	Sometimes (5–29%)
Enlarged and thickened heart muscle	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Acute kidney injury	Sometimes (5–29%)
Chronic kidney disease	Rarely (1–4%)

Abnormality of head or neck

Trait	How often it is seen
Chewing difficulties	Rarely (1–4%)

Abnormality of the digestive system

Trait	How often it is seen
Poor swallowing	Rarely (1–4%)

Abnormality of the respiratory system

Trait	How often it is seen
Exertional breathlessness	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 PYGM and how often each is seen. Find out more at hpo.jax.org.

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