Traits

Traits linked to BCS1L

BCS1 ubiquinol-cytochrome c reductase complex chaperone

The Human Phenotype Ontology links 77 traits to BCS1L, by body system: features seen in people with one of the gene's rare conditions.

BCS1L

Laboratory abnormality

Trait	How often it is seen
Abnormal urinary amino-acid findings	Always
Elevated lactate:pyruvate ratio	Always
High liver enzymes	Always
Increased lactate in body	Always
Low blood sugar	Always
Metabolic acidosis	Always
Microvesicular hepatic steatosis	Always
Recurrent low blood sugar levels	Always
Decreased transferrin saturation	Very often (80–99%)
Elevated serum ferritin	Very often (80–99%)
Fatty infiltration of liver	Very often (80–99%)
Increased iron concentration in liver	Very often (80–99%)
Renal Fanconi syndrome	Very often (80–99%)
Elevated alkaline phosphatase	Often (30–79%)
Elevated gamma-glutamyltransferase level	Often (30–79%)
High blood sugar	Often (30–79%)
High urine lactic acid levels	Often (30–79%)
Increased tyrosine in blood	Often (30–79%)
Severe lactic acidosis	Often (30–79%)
Chronic lactic acidosis	Not recorded
Elevated circulating iron concentration	Not recorded
Higher than normal levels of lactate in blood	Not recorded
Increased circulating pyruvate concentration	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Global developmental delay	Always
Degeneration of cerebellum	Often (30–79%)
Delayed CNS myelination	Often (30–79%)
Gliosis	Often (30–79%)
Intellectual disability	Sometimes (5–29%)
Ataxia	Not recorded
Can't control feelings	Not recorded
Degeneration of cerebrum	Not recorded
Depression	Not recorded
EEG abnormality	Not recorded
Epilepsy	Not recorded
Hallucinations	Not recorded
Increased reflexes	Not recorded
Mitochondrial encephalopathy	Not recorded

Abnormality of the integument

Trait	How often it is seen
Flattened and twisted hair	Always
Hair loss	Always
Lack of sweating	Always
Brittle hair	Very often (80–99%)
Sparse body hair	Very often (80–99%)
Fine hair	Often (30–79%)
Coarse hair	Not recorded
Dry hair	Not recorded
Hair shafts flattened at irregular intervals and twisted through 180 degrees about their axes	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone in trunk	Often (30–79%)
Low muscle tone, in neonatal onset	Sometimes (5–29%)
Breakdown of skeletal muscle	Not recorded
Generalized decreased muscle tone	Not recorded
Involuntary muscle stiffness, contraction, or spasm	Not recorded
Low muscle tone	Not recorded
Muscle weakness	Not recorded
Ragged-red muscle fibers	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Decreased liver function	Always
Periportal fibrosis	Always
Scar tissue replaces healthy tissue in the liver	Very often (80–99%)
Slowed or blocked flow of bile from liver	Very often (80–99%)
Bile duct inflammation	Not recorded
Decreased mitochondrial complex III activity in liver tissue	Not recorded
Feeding difficulties in infancy	Not recorded

Abnormality of the eye

Trait	How often it is seen
Abnormality of the eye	Often (30–79%)
Drooping upper eyelid	Often (30–79%)
Clouding of the lens of the eye	Not recorded
Rod-cone dystrophy	Not recorded

Abnormality of the genitourinary system

Trait	How often it is seen
Abnormality of the testis	Often (30–79%)
Underdeveloped penis	Often (30–79%)
Tubulointerstitial nephritis	Not recorded

Abnormality of the ear

Trait	How often it is seen
Sensorineural hearing impairment	Always
Hearing impairment	Very often (80–99%)

Growth abnormality

Trait	How often it is seen
Faltering weight	Always
Prenatal growth deficiency	Very often (80–99%)

Abnormal cellular phenotype

Trait	How often it is seen
Decreased activity of mitochondrial complex III	Always

Abnormality of head or neck

Trait	How often it is seen
Sparse or absent eyebrows	Very often (80–99%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Enlarged and thickened heart muscle	Not recorded

Abnormality of the endocrine system

Trait	How often it is seen
Decreased activity of gonads	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Decreased ability to exercise	Not recorded

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 BCS1L and how often each is seen. Find out more at hpo.jax.org.

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