Guide To Metabolic Disorders

October 30, 2023

Metabolism is a term used to describe a complex process that occurs in the body where energy is obtained from the food an individual has consumed. The food an individual consumes is made of three components called fats, proteins, and carbohydrates. These three components must be broken down into the substances that create fuel for the body, or sugars and acids. Once these substances have been made, they can be stored in body tissues like the muscles, fat, and liver, or they may be used right away as fuel.

A metabolic disorder forms when this process becomes disrupted by some mechanism involving abnormal chemical reactions. Some metabolic disorders have effects on the breakdown process of carbohydrates, lipids, and amino acids. Many individuals develop metabolic disorders when the associated organs become diseased, like the pancreas and liver. Different types of metabolic diseases produce varying effects on the body.

Gaucher Disease

Gaucher disease is a rare metabolic disorder that involves the deficiency of an important enzyme in the body that causes harmful quantities of specific lipids throughout the body. The deficiency of glucocerebrosidase allows the buildup of a lipid called glycolipid glucocerebroside in critical tissues like the liver, bone marrow, and spleen. Common complications of this metabolic disorder include hepatosplenomegaly, low platelet count, and low red blood cell count. Symptoms of these complications and others include easy bruising, excessive bleeding, weakness, pale skin, bone fractures, low muscle tone, muscle spasms, crossed eyes, difficulty with swallowing, and high-pitched breathing.

Mutations that occur in an individual's GBA gene are what cause Gaucher disease. This mutation is inherited from the individual's parents in an autosomal recessive fashion. Gaucher disease is diagnosed with the use of several blood panels, including an enzyme essay and other genetic tests. Treatment for Gaucher disease is highly individualized and often includes the direct replacement of missing enzymes.

Niemann-Pick Disease

Niemann-Pick disease is a condition where certain fats are not stored or removed from the body, resulting in numerous symptoms that affect the function of the liver, brain, spleen, and bone marrow. There are four different types of Niemann-Pick disease. Types A and B are the results of an improper production of acid sphingomyelinase or the enzyme that removes lipids from the cells in the body. The lipid that builds up in the tissues of those affected by types A and B Niemann-Pick disease is called sphingomyelin. Type C Niemann-pick disease is caused by a deficiency of the production of proteins that move large fat molecules between cells, allowing them to build in the cells.

The exact pathophysiology of type C Niemann-pick disease is not known due to its rarity, but it is known to be associated with too much sphingomyelin accumulation in the spleen, liver, and bone marrow. Diagnosis of Niemann-Pick syndrome types A, B, and E are made with blood tests and bone marrow biopsy. Type C Niemann-Pick disease is diagnosed with blood tests and skin biopsy. Treatment of Niemann-Pick disease is mostly supportive, as most cases are fatal before the patient reaches early to mid-adulthood.

Familial Hypercholesterolemia

Familial hypercholesterolemia is an inherited condition that causes an individual to have high cholesterol. Mutations in the FH genes located on different chromosomes are what causes an individual to have familial hypercholesterolemia. There are no symptoms in an individual who has high cholesterol until damage has been done to the blood vessels. Symptoms that occur in familial hypercholesterolemia precipitated tissue damage include chest pain with exertion, fatty deposits on multiple parts of the body, cholesterol deposits around the eyelids, and gray-white cholesterol deposits around the patient's corneas.

Blood tests are used to diagnose familial hypercholesterolemia in patients that measure levels of total cholesterol and low-density lipoprotein (LDL) cholesterol. Individuals are diagnosed by meeting criteria with total cholesterol levels over 260 milligrams per deciliter in children and 290 milligrams per deciliter in adults. Levels of LDL cholesterol in patients are over 155 milligrams per deciliter in children and 190 milligrams per deciliter in adults. Genetic testing may also be conducted to diagnose familial hypercholesterolemia. Treatment involves taking cholesterol-lowering medications and adhering to a strict diet.

Tay-Sachs Disease

Tay-Sachs disease is a disease seen primarily in infants that has adverse effects on the nervous system. It is a progressive neurodegenerative disorder and is fatal in almost all cases. This disease is caused by a genetic mutation on chromosome 15 that results in the absence of a protein referred to as hexosaminidase A. Brain cells are destroyed by a buildup of chemicals referred to as gangliosides when an individual does not have hexosaminidase A. Symptoms of infantile Tay-Sachs disease include decreased muscle strength, blindness, deafness, increased startle response, paralysis, seizures, slow growth, and spasticity.

Late-onset forms of Tay-Sachs disease produce symptoms such as muscle weakness, unsteady gait, tremors, slurred speech, and memory problems. Certain prenatal tests, including amniocentesis and chorionic villus sampling, can detect Tay-Sachs disease before an individual's birth. Blood enzyme analysis and eye exams are performed to diagnose late-onset forms of Tay-Sachs disease. There is no method of treatment for Tay-Sachs disease aside from palliative care with pain medication, anti-epileptics, feeding tubes, physical therapy, and respiratory care.


Phenylketonuria is an uncommon genetic condition that causes the accumulation of the amino acid referred to as phenylalanine in an individual's body. The production of essential neurotransmitters in the body, including norepinephrine, dopamine, and epinephrine, requires a compound called tyrosine. The enzyme phenylalanine hydroxylase is needed for the conversion of phenylalanine to tyrosine, and phenylketonuria patients do not produce an effective version of phenylalanine hydroxylase.

The buildup of phenylalanine causes symptoms like seizures, stunted growth, eczema, musty body and body fluid odor, tremors, hyperactivity, intellectual disabilities, irreversible brain damage, and behavioral problems. Phenylketonuria is diagnosed through a blood test performed on newborns when they are a few days old. The test involves using a lancet to draw blood from the heel of the baby to test for the mutations that cause phenylketonuria and other genetic diseases. Treatment involves going on a special diet that eliminates foods with phenylalanine in them and taking medications to lower levels of phenylalanine in the body.

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