Blue eyes. Brown Hair. Height. It’s all genetic, right? You may give your child his or her looks, but have you ever thought about what your genes do beyond the superficial level?
Let’s start with a basic genetics overview. Our genes are sections of our DNA that are written in a four-letter alphabet (A, T, C and G). We have more than 20,000 genes in every cell of our body. We have two copies of every gene; one is inherited from mom and the other from dad. Each gene has specific functions. You can think of them as the blueprint of our bodies. Some genes code for our eye color. Others help us process the food we eat, and others control our growth and development.
Sometimes developmental delay is unrelated to genetics. However, geneticists commonly see children with developmental delay, intellectual disability and autism spectrum disorder to determine if a child has an underlying genetic reason for their symptoms.
Phenylketonuria (PKU) is an example of a genetic disorder that, if left untreated, can cause developmental delay and intellectual disability. Patients with PKU are unable to process a specific amino acid component of protein, known as phenylalanine, which can cause brain damage if levels are too high. Phenylalanine is found in sodas, candy and all foods that have protein.
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PKU is treatable, which is why it is important to diagnose children with this disorder early, as a protein-restricted diet can prevent complications. The universal Newborn Screening Program is designed to screen every infant for treatable or preventable disorders, including those of the metabolism, such as PKU. Since the advent of the Newborn Screening Program in the 1960s, a countless number of patients with PKU have been identified and treated starting at birth.
There are many other genetic and non-genetic causes of developmental delay, intellectual disability and autism spectrum disorder. Although the genetic basis of autism and developmental delay has not been completely determined, there are tests available that can identify a genetic cause in approximately 20 percent of children with a clinical diagnosis. These tests can identify syndromes, such as Fragile X syndrome, a genetic condition associated with moderate or severe intellectual disability.
Fragile X is the most common genetic cause of autism in boys, also affecting males more severely than females. Early symptoms may be seen in childhood as developmental delay. These individuals can also have behavioral problems such as attention deficit hyperactivity disorder or sensory disorders.
There is currently no cure for Fragile X. Early intervention and therapies are useful in helping children reach their full potential. There is ongoing research to help improve the lives of those living with Fragile X. It is important that genetic professionals not only see the child for evaluation, but also discuss with the parents the chances of disorders occurring in future children.
Developmental delay and learning problems are not always genetic. Sensory problems, such as hearing or vision loss, can be the cause of delays. For example, a child with speech delay may actually be experiencing trouble hearing. A child with poor grades may have vision problems. It is important that these causes of developmental delay be addressed promptly because there are many recognized genetic and environmental causes leading to hearing or vision loss.
Genetics has implications for children much deeper than eye or hair color, and recent advances in technology have made new genetic testing available. This testing, known as whole exome or whole genome sequencing, looks at all 20,000 genes and can identify rare genetic disorders that may not have been previously considered. This testing can also help identify new syndromes and advance the field of genetics.
As we learn more about genes and their function, we will identify more causes of developmental delay, intellectual disability and autism spectrum disorders, and we will also continue working on developing novel treatment strategies to keep your children healthy.
Mustafa Tekin, M.D., is the chief of the Division of Clinical and Translational Genetics at the University of Miami Miller School of Medicine. Deborah Barbouth, M.D., is a pediatric clinical geneticist, and Dayna Morel is a genetic counselor at UHealth – the University of Miami Health System. For more information, visit UHealthSystem.com/patients/pediatrics.