Genetic Testing for Developmental Disorders

Developmental delay and disorders

Developmental delay is any noticeable and considerable delay in a child’s physical, cognitive, or social and emotional development. 

Some of the most well known, or most looked for examples of development delay, include late walking in an infant, delayed speech acquisition, and intellectual disability

Global developmental delay refers to delay that affects all areas of an infant or child’s development. A child diagnosed with global developmental delay will see significant challenges in several, if not all areas of their development. 

In other instances, a child may experience delay in just one area of their development, or in multiple areas but with only one specific skill. 

While there are globally, and medically, recognised developmental guidelines according to a child’s age, there is a degree of flexibility in terms of when children reach developmental milestones. Some children are naturally later walkers, and a delay in learning to walk as an isolated delay is not necessarily indicative of something more serious.

However an infant who is late to roll over, late to crawl, and late to walk, may be experiencing significant delay in their physical development. This pattern of delay may require further investigation.

Likewise if an infant is late to walk, and late to acquire speech, and delayed when it comes to mastering cognitive skills related to comprehension, so this identification of considerable delay in multiple areas of their development, may also warrant further investigation and targeted testing for developmental disorders. 

Developmental disorders

Developmental delay is a recognized sign of some neurological conditions, including autism. Children diagnosed with autism often display delay in their emotional and social skills, while also displaying specific behavioral tendencies. 

Developmental delay is also recognized as a potential symptom of rare disease. Pitt-Hopkins syndrome is just one example of a rare disease which presents with intellectual disability and a delay in reaching developmental milestones. 

Genetic testing for developmental disorders

A diagnosis of autism and/or developmental delay in a child may lead to a recommendation for a family to consider genetic testing, to rule out or confirm a genetic syndrome as the underlying cause. 

This may be recommended if a child is displaying other symptoms, or the unique facial features, characteristic of a specific genetic syndrome.

In general the type of genetic test recommended for children with developmental delay is chromosomal microarray (CMA). This is because it is currently recognized as providing the highest diagnostic success, with a diagnostic yield of around 15-20%. This makes it more accurate than karyotyping in individuals with developmental delay of unexplained origin or cause, and other symptoms or medical conditions. 

However this recommendation will also depend on a child’s current medical history, their family medical history, and anything else their genetic counselor may identify as relevant to their diagnosis. 

Genetic counseling

If a child is diagnosed with developmental delay, and it is considered significant enough to warrant further investigation into whether its origin is a rare disease or genetic syndrome, the first step in the process should be a referral to a genetic counselor.

A genetic counselor will be able to recommend the most appropriate form of genetic testing based on a child’s symptoms, type of developmental delay, the extent of the delay, and if there is any family history of genetic disease, or similar symptoms. 

They are also able to help families understand what the process of genetic testing involves, and what it might tell us about a child’s genetic and general health both in the short and long term. They are also able, crucially, to offer emotional support and counseling to parents and families involved in the process of investigating developmental delay in their baby or toddler. 

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