Living with Harel-Yoon syndrome
A rare mitochondrial condition starting in the newborn period or infancy, with developmental delay, low muscle tone, vision and nerve problems, and a thickened heart muscle.
Understanding Harel-Yoon syndrome
Features include global developmental delay, low muscle tone, intellectual disability, optic atrophy (damage to the vision nerve), nerve damage in the limbs (axonal neuropathy), thickened heart muscle (hypertrophic cardiomyopathy), and lactic acidosis. Other features vary and include spasticity, seizures, poor coordination, congenital cataract, and distinct facial features.
Signs & symptoms
Symptoms vary from person to person. GARD lists these among the most common:
- Global developmental delay
- Intellectual disability
- Low muscle tone in the trunk (axial hypotonia)
- Muscle stiffness (spasticity)
- Nerve damage in the limbs (peripheral axonal neuropathy)
- Poor speech
Not everyone has every symptom. GARD's list comes from the Human Phenotype Ontology.
Diagnosis
- 1Talk with your doctor
Share the symptoms you've noticed, when they started and your family health history. Notes and photos can help.
- 2See a specialist
Specialists who may be involved include brain and nervous system specialists, eye disease specialists, genetic specialists and heart and blood vessel specialists.
- 3Consider genetic testing
Changes in ATAD3A are linked to this condition. Genetic testing and counseling can help confirm a diagnosis and explain what it means for your family.
- 4Connect with expert centers
Children's Cardiomyopathy Foundation, United Mitochondrial Disease Foundation and MitoAction may keep lists of experts for this condition.
Care & treatment
- Care team
- Brain and nervous system specialists (neurologists); Eye disease specialists (ophthalmologists); Genetic specialists (geneticists); Heart and blood vessel specialists (cardiologists)
- Expert care
- Expert lists: Children's Cardiomyopathy Foundation, United Mitochondrial Disease Foundation, MitoAction
- Treatment
- GARD doesn't list specific treatments for this condition. Your care team will tailor care to your symptoms.
- Research
- Clinical trials and observational studies may be options. See the research section below.
General information, not medical advice. Your care team makes the decisions.
Everyday life
Living with a rare condition is easier with support.
- Connect with ATAD3A Patient Advocacy Alliance and other patient organizations
- Keep notes on symptoms, changes and questions for appointments
- Ask about patient registries that help research
- Look into financial aid and travel resources for care visits
Quick facts
Changes in the ATAD3A gene cause this condition. GARD lists autosomal dominant and mitochondrial inheritance.
Also known as: harel yoon syndrome; harel-yoon syndrome; hayos; hayos; ocular anomalies-axonal neuropathy-developmental delay syndrome; ocular anomalies, axonal neuropathy, developmental delay syndrome
Patient organizations
- ATAD3A Patient Advocacy AllianceHarel-Yoon syndrome · United States
- Children's Cardiomyopathy FoundationCardiomyopathy · United States
- United Mitochondrial Disease FoundationMitochondrial diseases · United States
- MitoActionMitochondrial diseases · United States
- The Foundation for Peripheral NeuropathyPeripheral neuropathy · United States
- Neuropathy Action FoundationPeripheral neuropathy · United States
You are more than your diagnosis
Perspectives from people navigating life with Harel-Yoon syndrome.
Explore research for Harel-Yoon syndrome
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- Recruiting studies from ClinicalTrials.gov
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- Eligibility is confirmed by the study team
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