Families often first notice 5p13 microduplication syndrome when a baby has low muscle tone that makes feeding or holding up the head harder than expected, or when developmental milestones like sitting, standing, or first words arrive later than peers. Doctors may spot the first signs of 5p13 microduplication syndrome during early check-ups because of low muscle tone, subtle facial features, or growth differences, and sometimes it’s first suspected after a developmental evaluation in toddler years. In some cases, the “first signs of 5p13 microduplication syndrome” are found through genetic testing done for unexplained developmental delay, learning differences, or autism traits rather than from a single visible feature.