Inherited Metabolic Diseases—Overview

Definition

This topic refers to rare genetic metabolic defects. When a defect occurs, it is because enzymes (proteins important for cells in your body to function correctly):

• Are missing from the body or
• Are not functioning normally

In some cases, extra chemicals or waste build up in the body. This causes symptoms. In other cases, there is a lack of vital substance or protein.

There are thousands of inherited metabolic diseases, such as:

• Tay Sachs
• Wilson’s disease
• Phenylketonuria (PKU)
• Lysosomal storage diseases

Causes

These diseases are caused by a genetic defect passed on from parent(s) to child.

Genetic Material

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Risk Factors

Risk factors include:

• Family history
• Certain ethnic backgrounds (Ashkenazi Jewish, Finnish, Dutch)

Symptoms

Symptoms can be severe and appear shortly after birth. Symptoms can also be mild and detected later in life. Tell your doctor if your child has any of these:

• Distorted facial features
• Enlarged tongue
• Cloudy eyes
• Purple-blue skin rash
• Swollen abdomen
• Skeletal deformities
• Short stature
• Lack of muscle control
• Seizures
• Decreased motor skills
• Developmental delays
• Intellectual disability

These symptoms may be caused by other conditions. If your child has any of these, talk to the doctor.

Diagnosis

The doctor will:

• Ask about your child’s symptoms and medical history
• Do a physical exam
• Work with specialists to diagnose the condition
• Order tests, such as:
  • Enzyme testing (skin, blood, urine)
  • Screening tests for vision and hearing
  • Electroretinogram—measures response of cells in the retina of the eye
  • Neuropsychological testing—measures mental function
  • MRI scan —a test that uses magnetic waves to make pictures of structures inside the brain, may be done along with another test called magnetic resonance spectroscopy (MRS)
  • Spinal tap —fluid is taken from the spine and examined
  • Tissue biopsy —a sample of tissues is taken and examined
  • Electromyogram (EMG)—measures electrical impulses in the muscles with a thin needle electrode
  • Other special tests of the heart, liver, and kidneys

Before your baby is born, prenatal tests can check for metabolic diseases.

Treatment

Talk with the doctor about the best treatment plan for your child. Treatment will depend on the type of condition your child has. Options may include:

Prevention

There is no way to prevent these kinds of disorders. Prenatal testing and newborn screening may help with early detection.