Most metabolic disorders in children can be due to inherited gene abnormalities (mutations or defects). However, a few can be acquired triggered by environmental and lifestyle factors such as childhood obesity. These conditions can alter normal physiological processes in the body due to defects in enzymes stimulating the process or the inability to use certain nutrients.
Read on to learn more about the causes, types, symptoms, and management of metabolic disorders in children and ways to cope with most of these inborn errors.
What Is A Metabolic Disorder?
In the case of a metabolic disorder, the defective genes might not be able to produce these enzymes or would be producing them in fewer quantities. This could cause disturbances in metabolism and lead to:
- A buildup of complex substances in the body, which could turn toxic.
- Inability to absorb essential nutrients into the body.
- Inability to synthesize building blocks of the body, such as carbohydrates, proteins, and fats to release energy.
It is important to identify the early symptoms of various metabolic disorders to ensure your child’s growth and development.
Causes Of Metabolic Disorders In Children
The main cause of most metabolic disorders in children is the inheritance of defective genes from the parents. These defective genes are due to mutations that might have occurred many years ago and are being passed down to generations.
The human body produces enzymes based on the information stored in several pairs of genes. Children usually get these genes from both the parents, and the child might receive one normal gene and one defective gene. The normal gene would function for the defective gene, and so, no symptoms of the disorder could be found in that child. However, that child could become the carrier and might pass on the defective gene to the next generation.
If the child inherits both the defective genes, then, their body would not be able to produce that particular enzyme, causing a metabolic disorder (1).
Sometimes, metabolic disorders could also occur due to environmental and lifestyle factors such as obesity.
Types Of Metabolic Disorders Found In Children
There are over 50 metabolic disorders identified in children; these disorders are due to defects in genes that are inherited from the parents. Here are a few details about a few such disorders.
|S.No||Name of the disorder||What is it?|
|1.||Galactosemia||Caused due to deficiency of galactose-1-phosphate uridylyltransferase (GALT), which is necessary for the metabolism of galactose, resulting in a build-up of sugars in the body. This is usually detected during newborn screening (2).|
|2.||Glycogen storage disease||In this condition, the body will not be able to metabolize the stored glycogen to supply energy and maintain steady blood glucose levels in the body. The children might have doll-like faces with fat cheeks, short stature, and bulging abdomen (3).|
|3.||Hereditary Fructose intolerance||The affected child would not be able to digest fructose or its metabolites (sugar, sorbitol, and brown sugar) due to deficiency of fructose-1-phosphate aldolase. This makes the children intolerant to fructose and accumulation of that sugar in the liver and kidneys (4).|
|4.||Pyruvate metabolism disorders||This can occur during infancy or could be developed later in life. In this condition, the body will not be able to metabolize pyruvate, which is a metabolite of glucose and helps in producing energy (5).|
|5.||Homocystinuria||This is characterized by the presence of excess homocysteine, which is a type of amino acid used in the synthesis of proteins. This usually occurs due to the reduced activity of cystathionine beta-synthase enzyme (6). As these amino acids are used for the synthesis of proteins, the child might fail to attain the ideal height and weight.|
|6.||Maple syrup urine disease||This metabolic disorder is characterized by urine and ear wax having a distinct odor resembling that of maple syrup. This is due to the body’s inability to produce certain enzymes required to break a type of amino acids. The signs of this disorder arise within a few hours of birth (7).|
|7.||Phenylketonuria||This metabolic disorder could be identified during newborn screening. In this condition, the baby lacks the enzyme phenylalanine hydroxylase that is necessary to synthesize the amino acid phenylalanine. As a result, the child might have a musty body odor and urine, caused due to the accumulation of phenylalanine, besides other symptoms (8).|
|8.||Tyrosinemia||This condition causes accumulation of the amino acid tyrosine due to the body’s inability to produce fumarylacetoacetate hydrolase, which is needed for the final breakdown of tyrosine (9). Symptoms vary from one person to another and may include failure to gain weight and grow as expected.|
|9.||Mucopolysaccharidoses (Lysosomal storage disorders)||This is a type of lysosomal storage disorder, where the lysosomes in the cells (present in the cartilage, tendons, corneas, and skin) lack the enzymes to break long-chain sugar carbohydrates. It has subtypes based on the enzyme that is lacking- MPS-I, MPS-II, and MSP-III, which are again subdivided based on the severity (10). Long-term effects of this disorder may affect the child’s appearance, physical abilities, organ development, and sometimes mental development.|
|10.||Mitochondrial disorders||These disorders occur due to the defects in the mitochondria of the cells in the body. As these mitochondria are known as powerhouses of the body, it could lead to developmental delays.|
Various syndromes that fall under this category are – Barth syndrome, chronic progressive external ophthalmoplegia, Kearns-sayre syndrome, Leigh syndrome, Mitochondrial DNA depletion syndrome, lactic acidosis, and Pearsons syndrome (11).
|11.||Menkes disease||This is a degenerative disorder of the body’s copper metabolism, which causes a deficiency of copper in the cells of the body, leading to retardation and stunted growth (12).|
|12.||Sickle cell disease||This disorder is caused due to the mutations in the gene related to hemoglobin. The red blood cells of the body have thickened walls, giving it a sickle shape, and have a shorter life than normal cells, causing anemia and repeated infections (13).|
Although most of the metabolic disorders are due to defective genes inherited by the child, childhood obesity could also be a triggering factor in some cases.
Metabolic syndrome: This syndrome is a cluster of risk factors such as high blood pressure, insulin resistance, cardiovascular risks. Although the exact cause for this syndrome is not yet found, obese children were found to be at a higher risk (14). Lifestyle and diet modification can reduce the risk in children.
Symptoms Of Metabolic Disorders In Children
The symptoms could be specific to the type of metabolism being affected. However, there are a few common symptoms that might help you identify if your child is suffering from a metabolic disorder.
- Poor feeding
- Not able to meet the growth milestones
- Abnormal urine, sweat, or saliva
- Mental retardation
- Abnormal body features (bulging abdomen, depressed nasal bridge)
- Kidney stones/ liver toxicity
- Failure to gain weight and height
- Abdominal pain and vomiting after consuming certain foods
- Eye problems – loss of vision , retinitis pigmentosa , optic atrophy , cherry red spot
- Extrapyramidal disorders
- Pyramidal and cerebellar syndrome with or without peripheral neuropathy (white matter disease)
- Joint and muscular disorders
Diagnosis Of Metabolic Disorders
Most of these metabolic disorders are diagnosed during newborn screening or before birth. Many states in the US have made it mandatory to screen babies for some of these disorders (15).
If any of the disorders are not diagnosed during the newborn screening, then they are not identified until the symptoms appear. Usually, your child’s doctor would perform a physical examination and run a blood and urine tests, and DNA test to determine the exact metabolic disorder.
Treatment For Metabolic Disorders In Children
As these disorders are due to defects in the genes, they cannot be completely cured with the treatment options available now. However, by taking certain measures, these disorders could be managed to a certain extent.
It should be remembered that your doctor is the best person to identify and prescribe the diet and precautions that would help your child to have a healthy childhood.
Your doctor might prescribe the following:
- Eliminating the food groups which the body is not able to process.
- Give artificial enzymes through medication in place of the inactive/ absent enzyme, which might promote proper metabolism.
- Give medications to remove the toxic products that get accumulated in the body due to failed metabolism.
Some of these disorders can cause serious complications and permanent organ damage in children, so early identification and intervention of metabolic disorders might help effective management.
Metabolic disorders in children mostly manifest due to the inheritance of defective genes from the parents. However, they can be treated upto a certain extent with the help of medical intervention. Take proper care of your child and ensure that they lead a healthy lifestyle. Taking care of your child suffering from such a disorder might be quite challenging and tricky. Therefore, strictly following the the doctor’s advice and taking medications as suggested by them will help you deal with these disorders in your child.
2. Galactosemia; Genetic and Rare Disease Information Center; National Center for Advancing Translational Sciences
3. Glycogen Storage Disease Type I; National Organization for Rare Disorders
4. Fructose Intolerance, Hereditary; National Organization for Rare Disorders
5. Pyruvate Dehydrogenase Complex Deficiency; National Organization for Rare Disorders
6. Homocystinuria due to Cystathionine Beta-Synthase Deficiency; National Organization for Rare Disorders
7. Maple Syrup Urine Disease; National Organization for Rare Disorders
8. Phenylketonuria; National Organization for Rare Disorders
9. Tyrosinemia Type 1; National Organization for Rare Disorders
10. Mucopolysaccharidoses Fact Sheet; Genetic and Rare Disease Information Center; National Center for Advancing Translational Sciences
11. Mitochondrial Myopathy Fact Sheet; Genetic and Rare Disease Information Center; National Center for Advancing Translational Sciences
12. Menkes Disease; National Organization for Rare Disorders
13. Sickle cell disease; Genetics Home Reference; US National Library of Medicine
14. Ram Weiss, Andrew A Bremer, and Robert H Lustig; What is metabolic syndrome, and why are children getting it?; NCBI
15. Recommended Uniform Screening Panel; Federal Advisory Committees; US Health Resources & Services Administration