Patients present with severe mental deficiency,
seizures, and delayed motor development associated with hypotonia. The
hypotonia eventually evolves in spasticity and joint contractures. Some of
the major features are the presence of macrocephaly, a high, broad forehead,
frontal cowlick, and long philtrum. They also have ocular hypertelorism with
epicanthal folds and down-slanting of the palpebral fissures. Many have some
form of anal anomaly, such as stenosis or imperforation, and complain of
chronic constipation. There are reports of patients with FG syndrome and
associated sensorineural deafness. Affected individuals may present with
minor skeletal anomalies involving fingers, toes, vertebrae, and sternum.
Occasionally, patients may have a fatal cardiac defect, with death prior to
age 2 years occurring in approximately one third of patients, mainly because
of bronchopulmonary and cardiac complications.