Homocystinuria (HCU)

Homocystinuria (HCU) is a rare genetic disorder present from birth. In HCU, the body is unable to break down an amino acid called methionine. This causes a build up of methionine and another amino acid called homocysteine in the eyes, brain, bones and blood vessels and can cause problems when untreated.

There are two different forms of HCU.

One form can be treated with Vitamin B6 supplements and this type is called ‘B6 responsive HCU’.

The other form of HCU cannot be treated with B6 supplements alone and this type is called ‘non-B6 responsive HCU’. At present, the treatment for ‘non-B6 responsive HCU’ is a protein restricted diet for life and taking regular dietary supplements which contain amino acids, vitamins and minerals. Supplementation of B6, B12, Folate, L-Cystine and Betaine may be recommended. The aim is to keep blood methionine and homocysteine levels within a specific target range.

At NCIMD, we have been treating patients with HCU since it was added to the National Newborn Screening Programme in 1971. Around 1 in 65,000 babies born in the Republic of Ireland has HCU. Most of our patients are ‘non-B6 responsive’ due to a common Celtic gene mutation.

Patients with HCU are managed by the multidisciplinary team and we liaise closely with the Metabolic Laboratory to ensure close and frequent monitoring of these patients. We follow international best practise guidelines in managing our patients with HCU. NCIMD have also been forerunners in the area of research in HCU. We have published many papers in international journals as well as presenting our experience of management of HCU at various international conferences. Dr. Crushell and Jenny McNulty (Dietitian) have been involved in the development of European Guidelines for the Management of HCU which are due to be published in 2016.

For patient stories click here

Printable Resources
HCU Dietary Handbook
1 gram Exchange list 2023
Slightly Higher Exchange List 2023 -for those on more than 7 exchanges

Super High Exchange List 2023 for those on more than 20 exchanges
Low Protein Manufactured Food List 2024
Reading food labels for other protein disorders
Reward Charts

HCU School letter

Weaning your baby on a diet for HCU

HCU Pharmacy Letter



Other resources
Harry and Heidi have HCU Storybook-a colourful and informative storybook about Harry and Heidi who have HCU has been developed by Jenny McNulty, Dietitian and Jill Moore, Play Specialist. This book focuses on the importance of the synthetic protein. If you would like a copy please contact us directly or ask for a copy at your next out-patient appointment. Harry and Heidi have HCU