Definition

X-linked adrenoleukodystrophy (X-ALD) is a multisystem disorder that primarily occurs in males. People with X-ALD cannot break down certain kinds of fats. The buildup of these fats can cause damage to the nervous system and adrenal glands.

X-ALD occurs when a certain protein is missing or not working. This protein is supposed to transport certain kinds of fats so they can be broken down. If they are not broken down, these fats can build up to toxic levels in the body. X-ALD is caused by one or more non-working ABCD1 genes.

Inheritance

In some families, a non-working gene happens for the first time in a child and was not inherited from a parent.

If inherited, X-ALD follows an X-linked pattern. The ABCD1 gene is located on the X-chromosome. Males have one X chromosome and one Y chromosome. One non-working ABCD1 gene is enough to cause X-ALD in males.

Females have two X chromosomes, and therefore a second copy of ABCD1. A female with one working and one non-working ABCD1 gene is called a “carrier." Female carriers can develop symptoms in adulthood and can pass the affected gene to their offspring..

Resources

• Baby's First Test
• Genetics Home Reference
• Family Ac​tion Sheet​
• Provider Action Sheet
  

Definition

Biotinidase deficiency (BD) is a metabolic disorder. In BD, the body cannot process a certain vitamin. This vitamin helps break down certain fats, proteins, and sugars from the diet.

BD occurs when a special protein, or enzyme, is not working well or missing. This enzyme helps process and recycle a certain vitamin so that it can be used. Having none of this vitamin available can lead to serious health problems. BD is caused by non-working BTD genes.

Inheritance

BD is inherited in an autosomal recessive pattern. This means that people with BD get one non-working BTD gene from each parent. People with two non-working BTD genes can have BD. Parents and other people with one working BTD gene and one non-working BTD gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Citrullinemia type I is a metabolic disorder. This disorder affects the body's ability to break down proteins from food.

Amino acids are “building blocks" that form proteins. Citrullinemia type I occurs when a special protein, or enzyme, is not working well or missing. This enzyme helps remove a certain chemical from the body. If not removed, this chemical can build up to harmful levels. Citrullinemia type I is caused by non-working ASS1 genes.

Inheritance

Citrullinemia type I is inherited in an autosomal recessive pattern. This means that people with citrullinemia type I get one non-working ASS1 gene from each parent. People with two non-working ASS1 genes can have citrullinemia type I. Parents and other people with one working ASS1 gene and one non-working ASS1 gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
  

Definition

Congenital adrenal hyperplasia (CAH) is caused by a group of endocrine disorders. This disorder These disorders affect the body's ability to make certain hormones.

CAH affects the adrenal glands. Adrenal glands are small organs that sit on top of the kidneys. They make several kinds of hormones. Hormone production is important for body function and growth.

Hormones are made by a series of chemical steps in the body. CAH occurs when a special protein, or enzyme, that performs one of these steps is missing or not working. The most common cause of CAH is non-working CPY21A2 genes. Other causes of CAH are non-working CYP11B1, CYP17A1, HSD3B2, CYP11A1, STAR, or CYPOR genes.

Inheritance

CAH is inherited in an autosomal recessive pattern. This means that people with CAH get one non-working CPY21A2 or other gene from each parent. People with two non-working CPY21A2 or other genes can have CAH. Parents and other people with one working and one non-working CPY21A2 or other gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Cystic fibrosis (CF) is a disorder that causes problems in the lungs, pancreas, and other organs.

CF is caused by non-working CFTR genes. The CFTR gene makes instructions for a protein that helps balance salt and water in certain cells. This balance is important for correctly producing mucus that covers and protects organs and tissues. If CFTR does not work correctly, the mucus is thicker than usual. This thickened mucus causes damage over time to the organs.

Inheritance

CF is inherited in an autosomal recessive pattern. This means that people with CF get one non-working CFTR gene from each parent. People with two non-working CFTR genes can have CF. Parents and other people with one working CFTR gene and one non-working CFTR gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Ac​tion Sheet
• Provider A​ction Sheet
  

Definition

Classic galactosemia is a metabolic disorder. In galactosemia, the body cannot process a certain sugar. This sugar is found in in many foods such as dairy products.

Galactosemia occurs when a special protein, or enzyme, is not working well or is missing. This enzyme normally breaks down a certain sugar to produce energy for the body. If the enzyme is not working, this sugar can build up to harmful levels in the body. Galactosemia is caused by non-working GALT genes.

Inheritance

Galactosemia is inherited in an autosomal recessive pattern. This means that people with galactosemia get one non-working GALT gene from each parent. People with two non-working GALT genes can have classic galactosemia. Parents and other people with one working GALT gene and one non-working GALT gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Glutaric acidemia type I (GA-I) is a metabolic disorder. GA-I affects the body's ability to use and break down proteins from food.

Amino acids are “building blocks" that form proteins. Multiple steps are needed to break down amino acids and their products. If not broken down, amino acids and related chemicals can build up to harmful levels in the body.

GA-I occurs when a special protein, or enzyme, that helps break down certain amino acids is missing or not working. GA-I is caused by non-working GCDH genes.

Inheritance

GA-I is inherited in an autosomal recessive pattern. This means that people with GA-I get one non-working GCDH gene from each parent. People with two non-working GCDH genes can have GA-I. Parents and other people with one working GCDH gene and one non-working GCDH gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Guanidinoacetate Methyltransferase Deficiency (GAMT) is a condition in which the body builds up a toxic chemical called guanidinoacetate (GUAC) and cannot make creatine. Without creatine, the body cannot store and use energy properly. This leads to brain, muscle, speech and behavior issues, and developmental delays. Symptoms may be seen anytime between 3 months to 3 years of age.

Inheritance

GAMT is an autosomal recessive disorder caused by pathogenic variants in the GAMT gene which is responsible for making GAMT enzyme. This enzyme helps convert guanidinoacetate (GUAC) into creatine which is needed for the body to store and use energy. Deficiency in the GAMT enzyme results in creatine deficiency and in the accumulation of GUAC in the cells. This leads to severe organ and tissue damage, particularly of the brain and muscles.

Resources

• Baby's First Test
• GeneReviews
  

Also known as

• ​Mult​iple carboxylase deficiency

Definition

Holocarboxylase synthase deficiency (HCSD) is a metabolic disorder. HCSD affects the body's ability to break down certain proteins and sugars from food.

Multiple steps are needed to break down parts of proteins and sugars. Each of these steps requires special proteins, or enzymes. If not broken down, related chemicals and other compounds can build up to harmful levels. 

Inheritance

HCSD is inherited in an autosomal recessive pattern. This means that people with HCSD get one non-working HLCS gene from each parent. People with two non-working HLCS genes can have HCSD. Parents and other people with one working HLCS gene and one non-working HLCS gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Primary congenital hypothyroidism (PCH) is an endocrine disorder. PCH affects the body's ability to make thyroid hormones.

The thyroid gland is located in the lower front of the neck. Thyroid hormones, which are made in the thyroid gland, are important for growth and development. In PCH, the thyroid gland can be missing, underdeveloped, or in the wrong place. The thyroid can also appear normal but may not make hormones correctly.

The cause for a missing or underdeveloped thyroid is often unknown. In less than 20% of cases, PCH is caused by non-working genes.

Inheritance

Most cases of PCH are not caused by genetic changes and are not inherited. This means PCH occurs in people with no family history of the disorder.

If PCH has a genetic cause, most cases follow an autosomal recessive inheritance pattern. This means that people with PCH get one non-working gene from each parent. People with two non-working genes can have PCH. Parents and other people with one working and one non-working gene are called “carriers." Carriers typically do not have symptoms.

More rarely, PCH follows autosomal dominant or X-linked inheritance. A medical specialist or genetic counselor can help determine which kind of PCH a person has.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Isovaleric acidemia (IVA) is a metabolic disorder. IVA affects the body's ability to use and break down proteins from food.

Amino acids are “building blocks" that form proteins. Multiple steps are needed to break down amino acids and their products. If not broken down, amino acids and related chemicals can build up to harmful levels in the body.

IVA occurs when a special protein, or enzyme, that helps break down a certain amino acid is missing or not working. IVA is caused by non-working IVD genes.

Inheritance

IVA is inherited in an autosomal recessive pattern. This means that people with IVA get one non-working IVD gene from each parent. People with two non-working IVD genes can have IVA. Parents and other people with one working IVD gene and one non-working IVD gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Long-chain L-3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is a metabolic disorder. In LCHAD deficiency, certain fats are not broken down to make energy.

Fats are needed to fuel the body, especially when fasting or ill. LCHAD deficiency occurs when a special protein, or enzyme, is not working well or missing. This enzyme is supposed to break down certain fats. LCHAD deficiency is caused by non-working HADHA genes.

Inheritance

LCHAD deficiency is inherited in an autosomal recessive pattern. This means that people with LCHAD deficiency get one non-working HADHA gene from each parent. People with two non-working HADHA genes can have LCHAD deficiency. Parents and other people with one working HADHA gene and one non-working HADHA gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Maple syrup urine disease (MSUD) is a metabolic disorder. This disorder affects the body's ability to use and break down proteins from food.

Amino acids are “building blocks" that form proteins. If not broken down, amino acids and related chemicals can build up to harmful levels in the body. MSUD occurs when special proteins, or enzymes, that are supposed to break down certain amino acids are missing or not working. MSUD can be caused by non-working BCKDHA, BCKDHB, or DBT genes. 

Inheritance

MSUD is inherited in an autosomal recessive pattern. This means that people with MSUD get one non-working BCKDHA, BCKDHB, or DBT gene from each parent. People with two non-working BCKDHA, BCKDHB, or DBT genes can have MSUD. Parents and other people with one working and one non-working BCKDHA, BCKDHB, or DBT gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a metabolic disorder. In MCAD deficiency, certain fats are not broken down to make energy.

Fats are needed to fuel the body, especially when fasting or ill. MCAD deficiency occurs when a special protein, or enzyme, is not working well or missing. This enzyme is supposed to break down certain fats. MCAD deficiency is caused by non-working ACADM genes.

Inheritance

MCAD deficiency is inherited in an autosomal recessive pattern. This means that people with MCAD deficiency get one non-working ACADM gene from each parent. People with two non-working ACADM genes can have MCAD deficiency. Parents and other people with one working ACADM gene and one non-working ACADM gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Mucopolysaccharidosis type I (MPS I) is a metabolic disorder. People with MPS I have trouble breaking down certain sugars in the body. If these sugars build up in organs and tissues, it can harm their ability to work normally.

MPS I occurs when a special protein, or enzyme, is not working well or is missing. This enzyme normally breaks down certain sugars. If the enzyme does not work well, these sugars will not be broken down and instead will build up. This can lead to health problems that can get worse over time. MPS I is caused by non-working IDUA genes.

Inheritance

MPS I is inherited in an autosomal recessive pattern. This means that people with MPS I get one non-working IDUA gene from each parent. People with two non-working IDUA genes can have MPS I. Parents and other people with one working and one non-working IDUA gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action She​et
  

Also knows as

• Hunter Syndrome
  

Definition

Mucopolysaccharidosis type II or MPS II prevents the body from breaking down sugars properly. This causes a range of symptoms that affect many parts of the body. Symptoms can include bone, muscle, heart, and lung problems, as well as developmental delays.

There are different forms of the disease, some more severe than others. The most severe form can appear in the first year of life. In a milder form, symptoms may not appear until later in childhood.

Inheritance

MPS II is an X-linked disorder caused by pathogenic variants in the iduronate 2-sulfastase (IDS) gene that results in accumulation of glycosaminoglycans (GAGs) in cells. This leads to progressive multisystem organ damage.

Resources

• Baby's First Test
• GeneReviews
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Classic phenylketonuria (PKU) is a metabolic disorder. This disorder affects the body's ability to use and break down proteins from food.

Amino acids are “building blocks" that form proteins. If not broken down, amino acids can build up to harmful levels in the body. PKU occurs when a special protein, or enzyme, that is supposed to break down a certain amino acid is missing or not working. PKU is caused by non-working PAH genes.

Inheritance

PKU is inherited in an autosomal recessive pattern. This means that people with PKU get one non-working PAH gene from each parent. People with two non-working PAH genes can have PKU. Parents and other people with one working PAH gene and one non-working PAH gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Pompe disease is a metabolic disorder. People with Pompe disease have trouble breaking down a certain sugar. This sugar can build up in organs and tissues which can harm their ability to work normally.

Pompe occurs when a special protein, or enzyme, is not working well or is missing. This enzyme normally breaks down a certain sugar. If the enzyme does not work well, the sugar will not be broken down and can build up. This leads to health problems that get worse over time. Pompe disease is caused by non-working GAA genes.

Inheritance

Pompe disease is inherited in an autosomal recessive pattern. This means that people with Pompe disease get one non-working GAA gene from each parent. People with two non-working GAA genes can have Pompe disease. Parents and other people with one working GAA gene and one non-working GAA gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action Sh​eet
  

Definition

Propionic acidemia (PA) is a metabolic disorder. PA affects the body's ability to break down certain proteins and fats from food.

Amino acids are “building blocks" that form proteins. Fatty acids are “building blocks" of fats. Multiple steps are needed to break down amino acids, fatty acids, and their products. If not broken down, related chemicals and other toxic compounds can build up to harmful levels.

PA occurs when a special protein, or enzyme, is missing or is not working. This enzyme helps break down certain amino acids as well as certain fatty acids. PA is caused by non-working PCCA or PCCB genes.

Inheritance

PA is inherited in an autosomal recessive pattern. This means that people with PA get one non-working PCCA or PCCB gene from each parent. People with two non-working PCCA or PCCB genes can have PA. Parents and other people with one working PCCA or PCCB gene and one non-working PCCA or PCCB gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  

Definition

Severe combined immunodeficiencies (SCID) are caused by a group of disorders that affect the immune system.

The immune system protects the body against infections, viruses, or “foreign" compounds. If the immune system is not working, common illness and infections can be life threatening. SCID can be caused by problems in genes such as IL2RG, ADA, IL-7, and JAK3. These genes usually affect the production of certain types of cells which are critical to immune response.

Inheritance

The most common form of SCID follows an X-linked recessive inheritance. The IL2RG gene is located on the X-chromosome. Males have one X chromosome and one Y chromosome. One non-working copy of IL2RG is enough to cause SCID in males. Females have two X chromosomes, and therefore a second working copy of IL2RG. A female with one working and one non-working IL2RG gene is called a “carrier." It is more common for males to have X-linked recessive SCID than females. A male typically inherits a non-working IL2RG gene from a “carrier" mother.

Other forms of SCID follow autosomal recessive inheritance. This affects males and females equally. In this type of inheritance, people have two copies of a gene that are not working. They typically get one non-working gene from each parent. Parents and other people with one working and one non-working gene are called “carriers." Carriers typically do not have symptoms.

A medical specialist or genetic counselor can help determine which kind of SCID a person has.

Resources

• Baby's First Test
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Sickle cell-beta thalassemia is a hemoglobin disorder. Hemoglobin disorders affect the body's ability to have healthy red blood cells.

Red blood cells bring oxygen from the lungs to every part of the body. Oxygen is stored in the red blood cell by the protein hemoglobin.

The gene HBB provides instructions to make hemoglobin. Sickle cell-beta thalassemia is caused by non-working HBB genes. Non-working HBB genes can lead to a lower overall amount of hemoglobin as well as red blood cells that can be stiff and “sickle" shaped. These red blood cells do not deliver oxygen as effectively and can cause health problems.

Inheritance

Sickle cell-beta thalassemia is inherited in an autosomal recessive pattern. This means that people with sickle cell-beta thalassemia get a non-working HBB gene from each parent. People with two non-working HBB genes can have sickle cell-beta thalassemia. Parents and other people with one working HBB gene and one non-working HBB gene are called “carriers." This is also referred to as having “trait." Trait is not a disease. People with trait typically do not have symptoms.

Resources

• Baby's First Test
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Sickle cell anemia is a hemoglobin disorder. Hemoglobin disorders affect the body's ability to have healthy red blood cells.

Red blood cells bring oxygen from the lungs to every part of the body. Oxygen is stored in the red blood cell by the protein hemoglobin.

The gene HBB provides instructions to make hemoglobin. Sickle cell anemia is caused by non-working HBB genes. Non-working HBB genes can lead to red blood cells that are stiff and “sickle" shaped. These abnormally shaped cells do not deliver oxygen as effectively and can cause health problems.

Inheritance

Sickle cell anemia is inherited in an autosomal recessive pattern. This means people with sickle cell anemia get a non-working HBB gene from each parent. People with two non-working HBB genes can have sickle cell anemia. Parents and other people with one working HBB gene and one non-working HBB gene are called “carriers." This is also referred to as having sickle cell “trait." Sickle cell trait is not a disease. People with sickle cell trait typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

S,C disease is a hemoglobin disorder. Hemoglobin disorders affect the body's ability to have healthy red blood cells.

Red blood cells bring oxygen from the lungs to every part of the body. Oxygen is stored in the red blood cell by the protein hemoglobin.

The gene HBB provides instructions to make hemoglobin. S,C disease is caused by non-working HBB genes. Non-working HBB genes can lead to red blood cells that are stiff and “sickle" shaped. These red blood cells do not deliver oxygen as effectively and can cause health problems.

Inheritance

S,C disease is inherited in an autosomal recessive pattern. This means people with S,C disease get a non-working HBB gene from each parent. People with two non-working HBB genes can have S,C disease. Parents and other people with one working HBB gene and one non-working HBB gene are called “carriers." This is also referred to as having “trait." Trait is not a disease. People with trait typically do not have symptoms.

Resources

• Baby's First Test
  
• Family Action Sheet
• Provider Action Sheet
  

Definition

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is a metabolic disorder. In VLCAD deficiency, certain fats are not broken down to make energy.

Fats are needed to fuel the body, especially when fasting or ill. VLCAD deficiency occurs when a special protein, or enzyme, is not working well or is missing. This enzyme is supposed to break down certain fats. VLCAD deficiency is caused by non-working ACADVL genes.

Inheritance

VLCAD deficiency is inherited in an autosomal recessive pattern. This means that people with VLCAD deficiency get one non-working ACADVL gene from each parent. People with two non-working ACADVL genes can have VLCAD deficiency. Parents and other people with one working ACADVL gene and one non-working ACADVL gene are called “carriers." Carriers typically do not have symptoms.

Resources

• Baby's First Test
• Genetics Home Reference​
  ​
  ​
  ​
  ​
  ​
  
  
  
  ​
  ​
  
  ​
  ​​​
  ​
  ​
  ​
  ​
  ​
  ​
  ​
  ​
  ​
  ​
  ​