Clinical evaluation of the floppy infant.

The list of possible diagnoses for floppiness in infancy is extensive, with potentially hundreds of rare diseases. Nonetheless, most floppy infants have distinctive features in the history, the family history, or the physical examination that quickly narrow the list to central or motor unit disorders, and often to specific diagnoses within these broad groups. Accurate diagnosis is important, as outcomes are similarly protean, genetic implications are frequent, and in some cases specific treatments are possible.