Depends on the age but for infants, they can have puffy face, dull look, thick tongue that sticks out.
For toddlers and children
, they can have constipation
, dry, brittle skin, poor feeding, short height
, fatigue, loss of muscle tone (floppy kids), choking
epidodes, low hairline
...This is a serious disease with serious lifetime consequences. It's easily checked by a blood test.