27th August 2020

A mother brings her 4-year-old son to clinic, because she is concerned he is not hitting his milestones

A mother brings her 4-year-old son to clinic, because she is concerned he is not hitting his milestones. He started walking at the age of 15 months – this did not initially cause the mother concern, as her older daughter started walking around this age, too. However, his development has since stalled, and unlike his peers, he is not yet able to run or jump. In the past two months, she has noticed he is having difficulty climbing the stairs. Notable findings on examination include bilateral calf enlargement. She has no other concerns regarding his development in other domains.

Which of the following is the most appropriate first-line investigation of this child? 

Select the SINGLE most appropriate option from the list below. Select ONE option only.