Traits

Traits linked to CYB5A

cytochrome b5 type A

The Human Phenotype Ontology links 66 traits to CYB5A, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the genitourinary system

Trait	How often it is seen
Ambiguous external genitalia	Always
Cleft of scrotum	Always
Scrotal hypospadias	Always
Decreased fertility	Very often (80–99%)
Enlarged ovaries with cysts	Very often (80–99%)
Hypospadias	Very often (80–99%)
Painful menstruation	Very often (80–99%)
Polycystic ovaries	Very often (80–99%)
Primary amenorrhea	Very often (80–99%)
Short penis	Very often (80–99%)
Small uterus	Very often (80–99%)
Decreased fertility in females	Often (30–79%)
Decreased fertility in males	Often (30–79%)
Decreased testicular size	Often (30–79%)
Underdeveloped vagina	Often (30–79%)
Undescended testes	Often (30–79%)
Abnormal sex determination	Sometimes (5–29%)
Ambiguous genitalia in males	Sometimes (5–29%)
Female external genitalia in individual with 46,XY karyotype	Sometimes (5–29%)
Male pseudohermaphroditism	Sometimes (5–29%)

Abnormality of the nervous system

Trait	How often it is seen
Abnormality of the nervous system	Often (30–79%)
Cerebral hypomyelination	Sometimes (5–29%)
Degeneration of cerebellum	Sometimes (5–29%)
Frontal cortical atrophy	Sometimes (5–29%)
Generalized brain degeneration	Sometimes (5–29%)
Global developmental delay	Sometimes (5–29%)
Intellectual disability, severe	Sometimes (5–29%)
Involuntary writhing movements in fingers, hands, toes, and feet	Sometimes (5–29%)
Limb dystonia	Sometimes (5–29%)
Severe global developmental delay	Sometimes (5–29%)
Temporal cortical atrophy	Sometimes (5–29%)
Delayed myelination	Rarely (1–4%)
Epilepsy	Rarely (1–4%)
Small basal ganglia	Rarely (1–4%)

Abnormality of the endocrine system

Trait	How often it is seen
Decreased circulating dehydroepiandrosterone-sulfate concentration	Always
Elevated circulating luteinizing hormone level	Always
Abnormal circulating corticosterone level	Very often (80–99%)
Absence of secondary sex characteristics	Very often (80–99%)
Decreased circulating androgen concentration	Very often (80–99%)
Decreased serum estradiol	Very often (80–99%)
Decreased serum testosterone level	Very often (80–99%)
Delayed puberty	Very often (80–99%)
Elevated circulating follicle stimulating hormone level	Very often (80–99%)
Hypergonadotropic hypogonadism	Very often (80–99%)
Primary gonadal insufficiency	Very often (80–99%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Delayed bone maturation	Very often (80–99%)
Low solidness and mass of the bones	Very often (80–99%)
Osteoporosis	Very often (80–99%)
Involuntary muscle stiffness, contraction, or spasm	Sometimes (5–29%)
Spastic tetraplegia	Sometimes (5–29%)
Spasticity and rigidity of muscles	Rarely (1–4%)

Abnormality of the integument

Trait	How often it is seen
Blue discoloration of the skin	Very often (80–99%)
Limited armpit hair	Very often (80–99%)
Sparse body hair	Very often (80–99%)
Sparse pubic hair	Very often (80–99%)
Abnormality of the nail	Often (30–79%)

Growth abnormality

Trait	How often it is seen
Short stature	Often (30–79%)
Faltering weight	Sometimes (5–29%)
Small for gestational age	Rarely (1–4%)

Abnormality of head or neck

Trait	How often it is seen
Lip discoloration	Often (30–79%)
Abnormally small head	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Blue outer white part of eyeball	Sometimes (5–29%)
Inward turning cross eyed	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Methemoglobinemia	Always

Abnormality of the breast

Trait	How often it is seen
Enlarged male breast	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Exertional breathlessness	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 CYB5A and how often each is seen. Find out more at hpo.jax.org.

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