Macroglossia, or a swollen tongue, is a relatively rare condition in children, according to WebMD. It is generally restricted to children who inherit certain genetic forms of the disease or children who develop macroglossia as a secondary condition to another disease. Diseases that may cause macroglossia include Down syndrome, Beckwith-Wiedemann syndrome and some cancers. Children may also develop macroglossia after experiencing trauma to the mouth or tongue.
Congenital macroglossia is transmitted as a dominant autosomal trait, notes WebMD. Autosomal dominance means that children of a parent with congenital macroglossia have either a 50 or 100 percent chance of inheriting the condition depending on whether or not their parent has one or two copies of the macroglossia-related genetic region. In the case of Beckwith-Wiedemann syndrome, a congenital disease resulting in overgrowth of many body parts, between 82 and 97 percent of children with the syndrome suffer from macroglossia, according to the Beckwith-Wiedemann Syndrome Support Group website.
Congenital forms of macroglossia can have both immediate and long-term effects on a child's development, according to the BWS Support Group. The precise effects vary from child to child, but difficulties with breathing and feeding are not uncommon. A child's ability to speak is usually not affected by macroglossia unless the child's tongue is extremely large.