Tyrosinaemia type I, II and III are rare metabolic disorders caused by enzyme deficiencies in the tyrosine catabolism pathway. Successful treatment is possible with the enzyme inhibitor NTBC (2 nitro 4 trifluoromethylbenzoyl 1,3 cyclohexanedione) in tyrosine type I and with dietary tyrosine and phenylalanine restriction in all three conditions.

Tyrosinaemia type I is the most severe disease of the catabolic pathway leading to progressive liver failure, renal tubular dysfunction and risk of hepatocellular carcinoma. Clinical presentation of Tyrosinaemia type II are skin and eye abnormalities, while neurological abnormalities have been reported in type III.

Treatment involves diet therapy. The aim of dietary treatment is to maintain plasma tyrosine concentrations below 600 µmol/l and above 200 µmol/l (normal reference range 30 - 120 µmol/l). A supplement of tyrosine/phenylalanine free amino acids is given at least three times daily. An allowance for tyrosine and phenylalanine must be included in the diet. A one gram protein exchange system is used i.e. the weight of food which provides one gram of protein.

Because of the limited range of foods allowed in the diet it is essential to supplement the diet with the full range of vitamins and mineral trace elements required for this age group of patients.

Current protein substitutes provide a good source of nutrition but they have several disadvantages;

• They have a low amino acid content, therefore a large bulk of powder is needed each day.

• It is recommended that they are given in large volumes of liquid. This makes it particularly difficult for the young patient to consume their recommended dosage.

• Existing products require careful weighing, measuring and mixing which makes transport and administration difficult especially for patients at school or in a social environment.

Vitaflo have developed a range of protein substitutes for patients with Tyrosinaemia - TYR Gel (1-10 years) and TYR Express (8 years +).

Currently the type of treatment available to this patient group is either large volume drinks or not nutritionally complete products and so a combination of products is required. These can be inconvenient and can lead to poor compliance.

TYR Gel and TYR Express have been specifically designed to be low volume nutritionally complete protein substitutes which have set a new standard of acceptance and convenience in this category of products.