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Amino Acid Disorders - Types, Symptoms, Diagnosis, and Treatment

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Amino acid disorders are genetic disorders in which the patient’s metabolism works inappropriately. This article explains amino acid disorders in detail.

Written by

Dr. Anahita Ali

Medically reviewed by

Dr. Kaushal Bhavsar

Published At September 29, 2022
Reviewed AtFebruary 14, 2023


The human body requires energy to function normally. The energy in the body is produced through metabolism, breaking down the food and releasing energy. Sometimes, this energy is used right away or stored in the body. There are various energy sources such as proteins, carbohydrates, fats, and so on.

When this metabolic process gets disturbed, it develops metabolic disorders. It means that the body fails to perform metabolism resulting in abnormal or inappropriate energy release. Without energy, the patient becomes fatigued, tired, and depressed, which may result in poor growth and development. These disorders are genetic, meaning that the defective genes are passed from the parents to their child; stay for a lifetime; are treated through dietary changes and supplements.

What Is an Amino Acid and Amino acid Disorder?

Amino acids are the building blocks that combine to form proteins. These are organic compounds present in the human body.

In addition, amino acid disorder is a genetic disorder in which the patient’s metabolism works inappropriately. It means the body’s ability to break the food and generate energy is affected.

What Does Amino Acid Do?

  • It breaks down vitamin B6 and tryptophan.

  • It helps in breaking down the food.

  • It helps in the growth and development of the body.

  • It repairs the tissues in the body.

  • It provides energy to the body’s muscles.

  • It strengthens immunity.

What Is the Classification of Amino Acids?

There are three groups of amino acids:

  1. Essential Amino Acids - They are not formed within the body and can be obtained from the food we eat. There are nine essential amino acids - histidine, leucine, isoleucine, lysine, phenylalanine, threonine, valine, and tryptophan.

  2. Non-Essential Amino Acids - They are formed within the body if the food does not contain these amino acids. There are eleven essential amino acids - alanine, arginine, asparagine, cysteine, aspartic acid, glutamic acid, glycine, proline, tyrosine, glutamine, and serine.

  3. Conditional Amino Acids - They are helpful only during illness or stress. There are eight conditional amino acids - arginine, cysteine, tyrosine, glutamine, ornithine, glycine, serine, and proline.

How Do Amino Acids Function in the Human Body?

The alanine cycle includes the following:

  • After intake of food, the proteins present in the food break down.

  • During this, large amounts of amino acids, such as alanine, are released into the blood and reach the liver.

  • The alanine transaminase enzyme in the liver converts the alanine into glutamate and pyruvate.

  • The pyruvate is further converted into glucose.

  • The glucose then flows into the blood and reaches the muscles to provide energy.

  • The amino acids of the alanine are converted into urea (an end or residual product of protein breakdown) which is excreted from the body.

What Are the Different Amino Acid Disorders?

Abnormal Metabolism - There are a few disorders related to the abnormal metabolism of amino acids. Metabolism is the energy creation and utilization by the body from food.

  • Phenylketonuria and maple syrup urine disease are common amino acid disorders.

  • In this condition, there is an incomplete breakdown of the amino acids in the body, or the amino acids may not reach the body's cells.

  • It results in the accumulation of harmful substances within the body.

  • It is a hereditary disorder.

Defects In the Urea Cycle - As urea is formed as a residual or end product of alanine conversion, any fault in this process or enzymatic activity may result in the accumulation of toxic substances such as ammonia in the blood.

  • It results in nausea, vomiting, and even a coma.

  • It is also a hereditary disorder.

Amino Acid Transport Disorder - It is characterized by the abnormal or defective transport of amino acids into the blood.

  • Generally, energy is required to transport the proteins into the blood.

  • Sometimes, the proteins have reduced transport activity, resulting in the loss of proteins through the urine.

  • It may also prevent the absorption of amino acids from the food.

Organic Acidemia - It is characterized by increased levels of organic acids in the body.

  • The organic acids accumulate in the tissues of the body and also in fluids such as urine.

  • It results in increased levels of acid in the patient’s blood.

  • It is commonly seen in small children or infants.

What Are the Symptoms of Amino Acid Disorders?

In general, the patient suffers from:

  • Poor or delayed growth and development. It is also called stunting.

  • Loss in weight.

  • Low energy levels.

  • Poor appetite.

  • Abnormal odor in sweating and urine.

  • Depression.

How Are Amino Acid Disorders Diagnosed?

The amino acid disorders are diagnosed through the following tests:

  1. Amino Acid Analysis, Plasma - A blood sample is taken from the patient, which is used to identify the presence of 36 types of amino acids. This test is done with the plasma.

  2. Amino Acid Analysis, Urine - A urine sample is taken, which is used to identify the amino acids taken in the diet. It identifies 40 types of amino acids.

  3. Amniocentesis - The levels of amino acids are sometimes tested before the baby is born. A sample of the fluid surrounding the baby inside the mother’s womb is taken and tested.

How Are Amino Acid Disorders Treated?

The treatment options are limited because these disorders are related to genetics. More common approaches include:

  1. A special diet with a low intake of amino acid or protein of which the patient is deficient. For example, if the patient has a deficiency of phenylalanine, the patient must take a diet low in protein content.

  2. Nutritional supplements that provide amino acids are suggested. The unique formula is recommended, which provides all the other necessary amino acids and nutrients to the patient.

  3. Medications are prescribed to treat other symptoms such as nausea, vomiting, depression, and so on.


Amino acid disorders affect the body's metabolic activity, resulting in an abnormal breakdown of food and low energy. This leads to incomplete body growth, low energy, fatigue, and many others. It is most commonly seen in infants or newborns and is diagnosed through newborn screening. These disorders do not have a definite treatment therapy.

However, dietary changes and a few medications may help deal with the condition. The proteins in the diet or food are the primary sources of amino acids. The dietary proteins are present in meat, nuts, beans, cereals, and many others.

Frequently Asked Questions


What Is the Common Type of Amino Acid Disorder?

There are various types of amino acid disorders. These are usually genetic disorders that affect the patient's metabolism. Out of various types of amino acid disorders, classic phenylketonuria is the most common type. People with this disorder have problems breaking down amino acids from the protein from the food.


What Type of Amino Acid Disorder Is Seen in Newborns?

Newborn babies with amino acid disorder are not able to process certain amino acids, and therefore, toxic substances start building up in the body soon after birth. This leads to damage to the brain and various organs. Tyrosinemia type I is the most severe form of this disorder that is usually seen in the first few months of life. Additionally, babies affected with this amino acid disorder are unable to thrive.


What Do Organic Acid Disorders Mean?

Organic acid disorders are a group of rare disorders that affect the metabolism of the body. Metabolism is the process by which the body changes food into energy. Children with organic acid disorders are unable to break down protein properly, which leads to the building up of harmful toxic substances in the blood and urine.


What Is the Cause of Amino Acid Disorder?

Amino acid disorders are hereditary disorders that occur due to genetic defects. These occur when the defective gene that causes the disorder is passed to the children, leading to the problem. The amino acid disorders can result from defects either in the breakdown of amino acids in the body or the inability of the body to get amino acids into the body cells.


What Leads to Amino Acid Deficiency?

Amino acid deficiency occurs when a person feeds on a low-protein diet for a long period of time, causing a fall in plasma levels of various essential amino acids. The low protein level in the body leads to devastating consequences during growth as amino acids are responsible for building muscles and causing chemical reactions in the body for metabolism, transporting nutrients, and preventing diseases. Additionally, amino acid deficiency is also seen in people with decreased immunity, digestive problems, fertility issues, lower mental alertness, depression, slowed growth in children, and other health problems.


What Are the Most Essential Amino Acids?

There are a total of nine of the most essential amino acids that have a very important role in body metabolism and performing other essential functions, which include: 
- Histidine.
- Isoleucine. 
- Leucine. 
- Lysine. 
- Methionine. 
- Phenylalanine. 
- Threonine. 
- Tryptophan. 
- Valine.


How Many Amino Acids Are There?

Roughly, there are around 500 amino acids in nature. Out of these, 20 amino acids are needed by the body. Nine of these amino acids are called essential amino acids, which are consumed by the food a person eats and can be found in a variety of foods like beef, eggs, and dairy.


What Are the Functions of Amino Acids?

Amino acids help in performing various functions, which include -
- Breaking down food.
- Growth of body tissue.
- Making hormones and brain chemicals (neurotransmitters).
- Provides energy.
- Helps in building muscles.
- Maintain healthy skin, hair, and nails.
- Boosting the immune system.
- Sustain a normal digestive system.


What Are Weak Acids?

Weak Acids are acids that do not completely segregate or dissociate into their constituent ions when dissolved in solutions. Some common examples of weak acids include -
- Formic acid.
- Acetic acid.
- Benzoic acid. 
- Oxalic acid.
- Hydrofluoric acid. 
- Nitrous acid.
- Sulfurous acid.
- Phosphoric acid.


What Is the Most Perfect Protein?

Animal-based foods such as meat, poultry, fish, eggs, and dairy foods are considered good sources of complete protein. On the other hand, plant-based foods such as fruits, vegetables, grains, nuts, and seeds often lack one or more essential amino acids. Therefore, it is always advised to consume animal-based food products to fulfill the body's protein needs.


Is Yogurt High in Amino Acids?

The protein present in yogurt is complete, which means it contains all nine essential amino acids. Additionally, it is also a high source of riboflavin, potassium, and vitamin B12. Depending on the type of nutrition requirement of the body, the person can choose the type of yogurt.


What Are the Clinical Features of Amino Acid Deficiency?

Amino acid deficiency can cause various signs and symptoms, which include: 
- Decreased immunity.
- Digestive problems. 
- Depression. 
- Fertility issues. 
- Lower mental alertness. 
- Slowed growth in children.


How to Check for Amino Acid Disorders?

Amino acid disorders can be diagnosed through the following tests:
- Amino acid analysis (Plasma) - Used to identify the number of amino acids in the plasma.
- Amino acid analysis (Urine) - Used to identify the number of amino acids in the urine.
- Amniocentesis - The level of amino acid in the unborn baby can be checked to identify any amino acid disorder.
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Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


amino acid disorders
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