This study investigates rare liver diseases that affect infants, children, and young adults. These diseases may involve problems with the liver's ability to process fats or energy, known as hepatic respiratory chain or fatty acid oxidation defects. The study aims to gather more information about these conditions and their impact on the liver and other parts of the body.

Participants will undergo various study procedures, which may include medical tests and assessments to understand the nature of their liver disease. The study may also involve checking for signs of mitochondrial disease, which is a condition that affects energy production in cells. Participants may have already had a liver transplant or show symptoms like lactic acidosis, hypoglycemia, or abnormal metabolic profiles.

• Who can participate: Children aged 0-18 years with suspected or documented liver-related diseases are eligible. This includes those with mitochondrial disease indicators, such as lactic acidosis or hypoglycemia, and those who have had a liver transplant.
• Study details: Participants will undergo medical tests and assessments to gather information about their liver disease and the impact of mitochondrial conditions on the liver and other body systems.