Families often first notice 17p11.2 microduplication syndrome in infancy or early childhood when a baby has low muscle tone that makes feeding, latching, or head control harder than expected, or when developmental milestones like sitting, first words, or walking arrive later. Doctors may first suspect it after a routine check-up notes small head size, subtle facial differences, or growth that’s below the curve, and a developmental evaluation raises concerns about speech, learning, or behavior. The “first signs of 17p11.2 microduplication syndrome” are usually confirmed with genetic testing such as chromosomal microarray when these early patterns prompt a referral.