Definition of XXXXX syndrome

XXXXX syndrome: A chromosome disorder in females, caused by the presence of five X chromosomes rather than the usual two. It is characterized by decreased intelligence (IQ 20 to 75) and multiple malformations including upward-slanting palpebral fissures (eyeslits), heart defect, and small hands with incurving fifth fingers. It is the most severe extra-X syndrome in females. Also known as the penta-X syndrome.