Date：2021-05-21

Developmental delay refers to children under the age of six who, due to various reasons, lag behind in various areas of normal child development. Developmental delay can affect an individual’s linguistic expression, motor skill, cognition, self-care and autonomy, and psychosocial ability. They can additionally affect several of those areas simultaneously. Though not a disease in itself, developmental delay can be linked to multiple medical conditions, including genetic factors (such as neurodegenerative rare diseases and Down syndrome), other diseases, pregnancy and childbirth factors (such as prenatal excessive drinking or childbirth complications affecting the newborn), and acquired environmental factors (such as exposure to toxic substances and malnutrition) etc. However, direct causes for most developmental delay cases are unknown.

Are there any early symptoms of neurodegenerative diseases that must be noted?

Neurodegenerative diseases are due to the gradual loss of neuronal function in the brain, leading to conditions such as dementia and movement disorders. There are many rare neurodegenerative diseases and their early symptoms are very similar, for example weakness of the limbs, poor center of balance, abnormal changes in personality and behavior, and linguistic difficulties. When symptoms of dementia and movement disorders from rare neurodegenerative diseases appear in children, these symptoms may be confused with developmental delays linked to other causes. As a result, it is important to note that symptoms which present as developmental delay may be due to the presence of a neurological disease.

Many potential factors contribute to developmental delay. Unfortunately, once a child is assessed to have delayed development, their guardians may mistakenly think that the child is simply "sluggish" and believe that with training and time, the child’s condition will improve. However, incidences of delayed development are not always as simple as that; in making such assumptions, guardians might overlook the early symptoms of neurodegenerative disease, and miss the time window for the early diagnosis of rare diseases. Some rare neurodegenerative diseases are early-onset and start to develop in childhood, such as spinal muscular atrophy, fibula atrophy, Rett's disease, Baker's muscular dystrophy, and Duchenne muscular dystrophy, amongst others. With the multitude of different possibilities, it is crucial for all factors to be considered when a child presents with developmental delay.

What should I do if I suspect that a child has a rare neurodegenerative disease?

As there are many rare neurodegenerative diseases with similar early symptoms, it is difficult to make an accurate diagnosis based on clinical symptoms alone. Approximately 80% of rare diseases are related to genetic inheritance. Identifying the genetic variants within the individual that are correlated with the disease can help correctly diagnose their rare neurodegenerative disease. Those who suspect that their child has a rare neurodegenerative disease should discuss with their doctor whether they should seek neurological genetic testing for their child. The sooner the correct diagnosis is made, the earlier effective disease control or treatment programs can be used, which will help mitigate the development of the disease within the individual before it causes further damage.