10 participants aged 3 years and over with tyrosinaemia or alkaptonuria will be prescribed Tyr sphere following an assessment of their individual needs by their dietitian.

All participants will enter a 4-week evaluation period, assessing adherence and gastrointestinal tolerance. Evaluations of Tyr sphere's palatability are made at the end of the evaluation period. Dried blood spots are taken on days 1 and 28 and once per week in between.

Participants who continue to take the product at the end of their evaluation period will enter a follow-up period during which metabolic control, anthropometric and nutritional status data will be collected during the yearly standard of care routine visits.

10 participants with tyrosinaemia or alkaptonuria will be invited to participate in this study. Following consent they will be assessed by their dietitian and a recommended amount of Tyr sphere will be prescribed based on their individual needs. Tyr sphere is a food for special medical purposes as defined by Regulation (EU) No 609/2013. It is designed to be prescribed based on its protein content, not its energy content.

Visit 1, baseline clinic visit activities: consent, demographics, anthropometric measurements, gastrointestinal history, dietary assessment, metabolic control assessment including collection of dried blood spots for phenylalanine and tyrosine levels, record routinely taken urine succinylacetone, serum albumin and pre-albumin levels, new dietary prescription.

Weeks 1 to 4 (patient at home): dried blood spots, adverse events reporting/assessment, daily Tyr sphere adherence diary, daily gastrointestinal symptoms diary (weeks 1 and 4 only), daily intake diary for Nitisinone which is routinely prescribed. There will be a telephone call

Visit 2, end of acceptability phase clinic visit activities: anthropometric measurements, review of diaries, review of adverse events, metabolic control assessment including collection of dried blood spots for phenylalanine and tyrosine levels, investigator's assessment of Tyr sphere for the participant and decision on continuing with the prescription.

Three-year routine follow-up: for the participants that do continue with the Tyr sphere prescription (in consultation with the investigator), they will enter a follow-up period of three years, during which only routine, standard of care visits and procedures will take place. Data will be collected on anthropometrics, phenylalanine and tyrosine levels from dried blood spots, adverse events, record routinely taken urine succinylacetone, serum albumin and pre-albumin levels.

Inclusion Criteria:

• Diagnosed with tyrosinaemia.
• Aged ≥ 3 years.
• In the opinion of the Investigator, can comply with the study protocol and take at least one sachet of the study product per day.
• Willingly given, written, informed consent from patient or parent/guardian.
• Willingly given, written assent (if appropriate).

Exclusion Criteria:

• Individuals who are allergic to milk, fish and soya (these allergens are inherent in the study product ingredients).
• Use of additional macro/micronutrient supplements during the evaluation period, unless clinically indicated and prescribed by the Investigator (must be recorded in patient case report form CRF).
• Women who are pregnant / breastfeeding at the start of the study or planning to become pregnant during the study.

N.B.: Women who become pregnant during the study will no longer be able to participate and will be withdrawn.

• Individuals who, in the opinion of the investigator, are unable to comply with the requirements of the protocol.
• Any co-morbidity, which, in the opinion of the Investigator, would preclude participation in the study.
• Patients who are currently participating in, plan to participate in, or have participated in an interventional investigational drug, food or medical device trial within 30 days prior to screening visit.