Traits

Traits linked to ISCA2

iron-sulfur cluster assembly 2

The Human Phenotype Ontology links 29 traits to ISCA2, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Absent speech development	Always
Global developmental delay	Very often (80–99%)
Loss of developmental milestones	Very often (80–99%)
Leukodystrophy	Often (30–79%)
Profound global developmental delay	Often (30–79%)
Vegetative state	Often (30–79%)
Dystonia	Sometimes (5–29%)
Elevated brain glycine level by MRS	Sometimes (5–29%)
Elevated brain lactate level by MRS	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Increased reflexes	Sometimes (5–29%)
Abnormal periventricular white matter morphology	Not recorded

Laboratory abnormality

Trait	How often it is seen
Elevated blood glycine levels	Sometimes (5–29%)
Higher than normal levels of lactate in blood	Sometimes (5–29%)
Increased CSF glutamate concentration	Sometimes (5–29%)
Increased CSF glycine concentration	Sometimes (5–29%)
Increased CSF lactate	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Optic atrophy	Always
Visual loss	Very often (80–99%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Visual impairment	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Involuntary muscle stiffness, contraction, or spasm	Always
Appendicular spasticity	Very often (80–99%)
Low muscle tone	Often (30–79%)
Generalized decreased muscle tone	Not recorded

Abnormal cellular phenotype

Trait	How often it is seen
Decreased activity of mitochondrial complex I	Always
Decreased activity of mitochondrial complex II	Sometimes (5–29%)
Decreased activity of mitochondrial complex IV	Sometimes (5–29%)

Abnormality of the immune system

Trait	How often it is seen
Recurrent respiratory infections	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 ISCA2 and how often each is seen. Find out more at hpo.jax.org.

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