Biochemical Genetics

Children with these disorders cannot use fats for energy. This can lead to low blood sugar, muscle weakness and heart problems. Medicines and special diets can treat many of these disorders. Examples are:

• Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency
• Very long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency

Many building blocks of the body, such as proteins, fats and other molecules, need to have sugars attached to them to work correctly. People with congenital disorders of glycosylation (CDG) cannot attach these sugars or sugar chains properly. Your child may have problems with growth and learning. The disorder may affect many parts of their body, including their brain, nerves, muscles, liver and immune system. Examples of CDGs include PMM2-CDG, ALG1-CDG, PIGT-CDG and MPI-CDG. In a disorder called NGLY1-CDDG, the body has trouble taking sugar chains off some proteins. Our clinic includes a Congenital Disorders of Glycosylation Center of Excellence.

Carbohydrates are a key part of our diet that provide energy. Problems with how a child’s body breaks down or uses carbohydrates can cause a harmful amount of carbohydrate to build up in their body. This can lead to health problems. Examples include:

• Glycogen storage disorders, a problem with how the body stores or breaks down glycogen
• Galactosemia, where the body cannot properly break down a sugar molecule called galactose found in dairy products

In these disorders, complex sugars build up in small sections inside cells, called lysosomes. The buildup makes the cells swell and stops the cells from working right. The different lysosomal storage disorders (LSDs) affect different body systems and cause different symptoms. Some LSDs can be treated. Our clinic includes a Lysosomal Storage Disorder Center of Excellence.

Examples of LSDs are:

• Gaucher disease
• Pompe disease
• All types of mucopolysaccharidosis (MPS)
  • Morquio syndrome
• Fabry disease
• Tay-Sachs disease

These disorders affect how the body makes energy. They can involve many body systems. Most often they affect the heart, brain and muscles. Examples include:

• Mitochondrial encephalomyopathy lactic acidosis and stroke-like episode (MELAS)
• Alpers disease
• Barth syndrome
• Leigh syndrome
• Respiratory chain complex deficiency

Read about Seattle Children’s Mitochondrial Medicine and Metabolism Clinic.

Peroxisomes are part of the cell that are key to biochemical reactions such as metabolizing fatty acids and making lipids. In these disorders, either the body does not make peroxisomes or they do not work right. The disorders can affect many body systems. Most often they involve the eyes, brain, liver, kidneys and bones.

Examples include:

• X-linked adrenoleukodystrophy
• Zellweger spectrum disorders
• Refsum disease

Children with these disorders cannot use protein for energy. This can cause toxic acids to build up in their bodies. They may then have problems with growth, learning and overall health. Medicines and special diets can treat many of these disorders. Examples of organic acid disorders are:

• Propionic acidemia (PA)
• Methylmalonic acidemia (MMA)
• Glutaric acidemia types I and II

Amino acids are "building blocks" that join together to form proteins. Children with an amino acid disorder may have trouble breaking down certain amino acids or getting the amino acids into their cells. These problems cause a buildup of harmful substances in the body and can lead to serious health problems.

Children with these disorders cannot use protein properly for energy. This can cause toxic by-products to build up in their bodies. The buildup can lead to problems with growth, learning and overall health. Medicines and special diets can treat many of these disorders.

Examples of urea cycle disorders are:

• Ornithine transcarbamylase (OTC) deficiency
• Arginase deficiency
• Citrullinemia

Purines and pyrimidines form the bases of our DNA, help with our body’s immune response and help the cell make energy. Children with a purine or pyrimidine metabolism disorder could have problems with their learning, behavior, immune system or growth. They may have anemia and react to certain medications. Lesch-Nyhan disease and adenylosuccinase deficiency are examples of these disorders.

Children with Wilson disease cannot get rid of copper they get from food but do not need. Most children's bodies filter out this extra copper. But in children with Wilson disease, the copper builds up and can damage their liver, brain and other organs. Medicines and diet changes can treat Wilson disease if it is diagnosed early.

Our clinic includes a Wilson Disease Center of Excellence. Dr. Sihoun Hahn, director of our Wilson Disease Center of Excellence, has created a test to detect this condition. He is working to have the test included in newborn screening so babies can be treated before the disease causes harm. Read more.

Many children born with metabolic diseases need lifelong care. This helps them do the best physically and mentally and have the highest possible quality of life.

We give your child a full diagnostic evaluation and comprehensive care. This includes:

• Testing for newborns who have abnormal results from Washington state newborn screenings
• Complete nutritional assessments
• Long-term metabolic management along with dietary treatments
• Genetic counseling for children and adults with suspected or diagnosed inherited metabolic disorders
• Connecting you and your family to resources in our hospital and community
• Support from social workers to help you and your child adjust to and cope with having a lifelong metabolic disease

Some metabolic diseases happen because a child has an enzyme that is not normal. This causes sugars and proteins to build up in the body. In enzyme replacement therapy (ERT), we give your child the enzyme they need through an intravenous (IV) line. This process is called infusion.

ERT treats the symptoms of the disease but does not cure the disease. It helps treat some lysosomal storage disorders:

• Gaucher disease
• Fabry disease
• MPS I
• MPS VI
• Glycogen storage disease type II (or Pompe disease)

Nutrition therapy is often the cornerstone of medical treatment. Our dietitians and doctors partner to provide the best nutrition plan for each patient. We tailor a nutrition plan for your child to:

• Help them achieve their full growth and development
• Provide the nutrients they need
• Modify carbohydrates, proteins or fat (macronutrients) as needed for their disorder

We teach your child and family about their nutrition plan and provide support. We help manage diets by mouth, through feeding tubes or by IV into a vein if needed during acute illness.