As the name suggests, Inherited metabolic disorders refer to different types of medical conditions caused by genetic defects — most commonly inherited from both parents — that interfere with the body’s metabolism (complex set of chemical reactions that the body uses to maintain life, including energy production).While inherited metabolic disorders are individually rare, they are collectively common. Single gene defects result in abnormalities in the synthesis or degradation of proteins, carbohydrates, or fats. Most are due to a defect in an enzyme or in a transport protein, resulting in a block in the way the compounds are processed by the body. Severe effects are due to the toxic accumulations of molecular debris. Special enzymes break down food or certain chemicals so that the body can use them right away for fuel or store them. Also, certain chemical processes break down substances that the body no longer needs, or make those it lacks. When these chemical processes don’t work properly due to a hormone or enzyme deficiency, a metabolic disorder occurs. Inherited metabolic disorders fall into different categories, depending on the specific substance and whether it builds up in harmful amounts (because it can’t be broken down), it’s too low, or it’s missing. Some metabolic disorders can be diagnosed by routine screening tests done at birth. Others are identified only after a child or adult shows symptoms of a disorder.
The timely diagnosis of inherited metabolic disorder is essential as in many cases children are misdiagnosed as patients of cerebral palsy, autism or other conditions whose symptoms can be similar to inherited metabolic disorders.
Treatment for an inherited metabolic disorder depends on the type and severity, how much the disorder affects body or brain functions and other considerations. Because there are so many types of inherited metabolic disorders, treatment recommendations may vary considerably — from dietary restrictions, certain vitamins or other therapies to medication or surgery.
Tests and assessments may include a biopsy of the skin or other tissue, magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), spinal tap (lumbar puncture), and an electromyography (EMG), which includes a nerve conduction study. In tests that involve radiation, specialists carefully monitor doses to avoid the risk of radiation overexposure.
Other tests and evaluations may include:
- Genetic evaluation and testing: Specialists perform a thorough physical exam and discuss family history. They may also order genetic testing and provide genetic counseling.
- Neurological assessment: For children with neurological problems, specialists perform various tests, including an extensive physical exam and certain screenings, such as vision, hearing, heart and liver. The exam will include a detailed medical history of the child and the extended family. Older children, teens and adults may also receive neuropsychological testing.