About Classical Homocystinuria

What is Homocystinuria?

The disease

Homocystinuria is an autosomal recessively inherited disorder. This means that an individual inherits the same defective gene for the same trait from each parent.


Homocystinuria is a metabolic disease affecting the trans-sulfuration pathway or methylation pathway.  Classical Homocystinuria, the most common form of Homocystinuria, is caused by a deficiency in the enzyme known as Cystathionine Beta-Synthase (CbS).  The lack of the enzyme prevents the body from processing methionine, an essential amino acid, from food containing protein.  As a result toxic levels of harmful substances accumulate in the body and cause serious health problems.

There are multiple forms of Homocystinuria, each distinguished by their clinical signs and symptoms and underlying genetic basis.

Classical Homocystinuria affects at least 1 in 200,000 to 335,000 people worldwide.  The incidence of the rarer forms of Homocystinuria are unknown.

Download HCU Disease Checklist

The symptoms

Homocystinuria is progressive and affected individuals suffer multi-systemic disorder of the central nervous system (CNS), ocular, skeletal, and cardiovascular system.  Symptoms are highly variable but include intellectual disability, developmental delay and learning difficulties, psychiatric disturbances, behavioural problems, dislocation of the lens of the eye resulting in blindness if untreated, seizures, osteoporosis and skeletal abnormalities, premature heart attack and stroke.  As a whole, the complications of the disease lead to a reduced quality of life and significantly shorter life expectancy.

The treatments

No cure has been discovered for Homocystinuria.  However, nearly one half of individuals affected with Homocystinuria benefit from Vitamin B6 supplementation.  For the remainder, the current mainstay of treatment is a strict low protein diet coupled with supplementation with B6, B12, folate, and Betaine together with a ‘medical formula’.  This treatment regime aides in the restoration of metabolic balance in the affected individual.

Focus of treatment in the newborn period is to ensure the development of normal intelligence and the prevention of the development of other complications of the disease.  When treatment is commenced later, the aim is to prevent further escalation of the complications already present.

HCU info resources

Meeting Resources

Faces of hope. Stories of hope.

Submit a story

Regardless of whether you are an individual affected by HCU, a carer, family member, friend or volunteer we would love you to share your story. Sharing your story helps to strengthen the HCU community and to share experiences. Share your story today and make a difference.

By submitting this form you give consent for HCU Network Australia to use this story and imagery on its website and for marketing purposes

Clinics in Australia

South Brisbane
North Adelaide


Children’s Metabolic Clinic
The Children’s Hospital, Westmead
Hawkesbury Rd & Hainsworth St, Westmead, Sydney, NSW
ph. (02) 98452525

Adult Metabolic Clinic
Westmead Hospital
Cnr Darcy Rd & Bridge St, Westmead, NSW 2145
ph. (02)98459780


Children’s Metabolic Clinic
Women’s and Children’s Hospital
72 King William Rd, North Adelaide SA
ph. (08) 8161 7295

Adult Metabolic Clinic
Royal Adelaide Hospital
North Terrace, Adelaide SA
ph. (08) 8222 5174


Children’s Metabolic Clinic
Royal Children’s Hospital
50 Flemington Road, Parkville VIC
ph. (03) 9345 6180

Adult Metabolic Clinic
Royal Melbourne Hospital
300 Grattan St, Parkville VIC
ph. (03) 9342 7074


Children’s Metabolic Clinic
Princess Margaret Hospital
Roberts Rd,
Subiaco WA
ph. (08) 9340 8222

Adult Metabolic Clinic
Royal Perth Hospital
Perth WA
ph. 1300 855 275


Children’s and Adult Metabolic Clinic
Lady Cilento Children’s Hospital
501 Stanley Street, South Brisbane QLD
ph. (07) 3068 1111


HCU Network Australia Blue Bag

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A diagnosis of a rare disease can change a family’s life. Our HCU Blue Bag seek to provide practical support to alleviate some of the emotional stress and isolation experienced by the individual and their families at the time of diagnosis.

We invite you to take a virtual look inside our Blue Bag. It is a toolkit full of resources for newly diagnosed individuals and their families. Email us if you haven’t received your Blue Bag at your Australian metabolic clinic.

Check your contact information is up to date on our Contact Registry and download or print our Contact Register Postcard
Correct contact details mean you will be kept updated of the latest news and events.
Download or print HCU Network Australia Flyer
A snapshot about HCU Network Australia aims, objectives and available resources.
Download or print HCU Disease Checklist – Homocystinuria: A treatable disorder
A comprehensive list of the key warning signs and symptoms of classical homocystinuria. This could help you speak with your doctor about your symptoms. Take the interactive Checklist along to your next appointment.
Download or print The Patient Information Booklet: Classical Homocystinuria – a treatable disorder and Quick Guide
The Patient Information Booklet combines the Guidelines for the diagnosis and management of cystathionine beta-synthase deficiency together with other relevant information into one booklet for people with HCU to read and share with others.  The Quick Guide summarises key points from the Patient Information Booklet.
Download or print AccuGo for HCU Brochure
AccuGo is a smartphone App designed to ease the day to day management of the low protein diet and is a service provided by HCU Network Australia.
Download or print The Patient Information Booklet: Classical Homocystinuria – a treatable disorder (Brazilian Portuguese Translation) and Quick Guide (Brazilian Portuguese Translation)
The Patient Information Booklet combines the Guidelines for the diagnosis and management of cystathionine beta-synthase deficiency together with other relevant information into one booklet for people with HCU to read and share with others. The Quick Guide summarises key points from the Patient Information Booklet.
HCU Network Australia portfolio.
A portfolio to collate medical letters, reports and results. Tabs include blood results, reports, metabolic correspondence, specialist correspondence and notes.
Hugo the Rare Rhino.
Hugo is our branded soft plush white rare rhino. For the younger patients when cuddles are needed.
Join our Patient Forum, watch Patient Testimonials and read Patient Stories.
Submit your patient story here
Visit our HCU Network Australia Youtube Channel for Meeting presentations and expert Q & A
Subscribe to our Youtube Channel to be alerted when new video resources become available.
Watch expert Webinars on topics of interest
Past Webinar recordings are available to view here.
Check out Meeting Resources from past International Patient – Expert Meetings
If you are unable to attend our conferences in person you can view some of the presentation slides here.











Fact Sheets & Infographics

  • What is Classical Homocystinuria?

View our animated infographic here.

  • What is Classical Homocystinuria Factsheet

Coming Soon!

  • Classical Homocystinuria Infographic

An overview of diagnosis, symptoms and treatment. Download or print PDF here.

  • Investigational Therapies Research Map

An overview of clinical and preclinical stage technologies in development for HCU. Download or print PDF here.

  • Key priorities for future research and patient advocacy

An overview of our 3 key focus areas. Download or print PDF here.

  • Are you missing a treatable disorder? Classical Homocystinuria. Key warning signs and symptoms

Coming Soon!

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Healthcare professionals