Do Inherited Metabolic Disorders (IMDs) Cause Disability?




What is Disability?

The Social Security Administration’s impairment listing manual (called the blue book) lists a number of impairments, both physical and mental, that will automatically qualify an individual for Social Security disability benefits (SSDI) or Supplemental Security Income (SSI), provided the individual’s condition meets, or is equivalent to, the specified criteria for a listing. The listing manual, which has been updated for 2017, includes:

  • musculoskeletal problems, such as back injuries
  • cardiovascular conditions, such as heart failure or coronary artery disease
  • senses and speech issues, such as vision and hearing loss
  • respiratory illnesses, such as COPD or asthma
  • neurological disorders, such as multiple sclerosis, cerebral palsy, Parkinson’s disease, and epilepsy
  • mental disorders, such as depression, anxiety, schizophrenia, autism, or retardation
  • immune system disorders, such as HIV/AIDS, lupus, and rheumatoid arthritis
  • various syndromes, such as Sjogren’s Syndrome and Marfan Syndrome
  • skin disorders, such as dermatitis
  • digestive tract problems, such as liver disease or IBD
  • kidney disease and genitourinary problems, and
  • cancer
  • hematological disorders, such as hemolytic anemias and disorders of bone marrow failure


What is Inherited Metabolic Disorders?

Inborn Errors of Metabolism (IEM) or Inherited Metabolic Disorders (IMDs) are individually rare but collectively will make frequent appearances in a busy pediatric ICU. The signs and symptoms of IEMs may be nonspecific and asymptomatic. They often overlap extensively with more common disorders. When symptoms show of the IEMs; screening should be done.


Did you know that Inherited Metabolic Disorders (IMDs) cause disability?

I collected a few evidences from few references while conducting a research about it and I found that:

  • Treatment for MCAD deficiency is relatively simple with dietary management, thus preventing possible early death and neurological disability. After (early) diagnosis, current management makes death rare and improves outcome.
  • The average UK incidence of PKU (classical and atypical combined) is 11.0 cases per 100,000 live births. Early dietary interventions, including dietary treatment before or during pregnancy, are effective in reducing the severity of developmental delay, and neonatal screening using tandem MS is suitable for the reliable detection of PKU.
  • Mitochondrial disorders generally demonstrate multisystem involvement because of the presence of mitochondria in all cells. However, sometimes only single-organ systems appear clinically affected. Signs and symptoms referable to the skeletal and cardiac muscle systems should always be suspect. Children with developmental delay or intellectual disability and hypotonia of unknown etiology in which extensive work-up has ruled out other inborn errors of metabolism and genetic syndrome causes often fall into this category. Other CNS signs may include seizures, ophthalmoplegias, ataxia (which may be intermittent rather than chronic), strokelike episodes, and cranial nerve dysfunction. Blindness with a variety of ophthalmoscopic abnormalities and sensorineural deafness may be present. Other organs may show symptoms manifesting as feeding disorders, intermittent vomiting episodes, failure-to-thrive, severe constipation or chronic abdominal pain, liver or kidney disease, diabetes, thyroid dysfunction, and respiratory dysfunction. Clinical presentations may be of acute severe metabolic illness with severe acidosis, with or without hypoglycemia, and severe CNS depression or a more indolent, chronic type of picture with poor growth and development.
  • In a storage disease Von Gierke’s disease (glycogenosis type I), hypoglycemia causes many of the clinical difficulties seen in patients during the first year of life. In this period seizures are frequent, and long‐standing hemiplegia and mental retardation occur. Failure to thrive, xanthomas, and isolated hepatomegaly are common, and excessive subcutaneous fat over the buttocks, breasts, and cheeks develops. Affected children usually have a protruding abdomen due to enlargement of the liver. Patients often have recurrent stomatitis frequent infections and may have isolated chronic inflammatory bowel disease.
  • Classic Galactosemia is due to a deficiency in the enzyme galactose-1-phosphate uridyltransferase (GALT). The initiation of lactose (glucose and galactose)-based feedings in the newborn who has galactosemia leads rapidly to metabolic decompensation, with liver dysfunction, jaundice, and coagulopathy. Late-diagnosed infants who survive the initial episode of metabolic decomposition often develop intellectual disability.


Can the IMD Caused Disabilities Be Treated?

Further confirmatory testing often is necessary if Newborn Screening laboratory tests point toward a specific disease. Confirmatory testing and disease-specific therapy should be conducted following consultation with a biochemical genetics specialist. If detected and treated early, the clinical outcome for many IEMs can be favorable and the affected may live a relatively normal life. In a study conducted in 2012, it was found that a considerable proportion of treatable IDs (62%) can be reliably detected through a panel of metabolic screening tests on blood (total homocysteine, plasma aminoacids) and urine (organic acids, purines and pyrimidines, creatine and guanidinoacetate, glycosaminoglycans, oligosaccharides). In general these tests are offered by most biochemical genetics laboratories around the world at affordable prices and with considerable yield per test.

“Genetic etiologies constitute the most frequent cause and are demonstrable in more than 50% of individuals with ID.” Van Karnebeek, C. D., & Stockler, S. (2012).

Treatments for genetic metabolic disorders follow a few general principles:

  • Reduce or eliminate intake of any food or drug that can’t be metabolized properly.
  • Replace the enzyme or other chemical that is missing or inactive, to restore metabolism to as close to normal as possible.
  • Remove toxic products of metabolism that accumulate due to the metabolic disorder.

Treatment may include such measures as:

  • Special diets that eliminate certain nutrients
  • Taking enzyme replacements, or other supplements that support metabolism
  • Treating the blood with chemicals to detoxify dangerous metabolic by-products





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