Genetically transmitted polymalformative syndrome
characterized by short stature with a disproportionately large head,
imperforate anus, hypotonia, and agenesia of corpus callosum.
FGS I Syndrome; Keller Syndrome; Opitz-Kaveggia Syndrome;
Megalocornea-Mental Retardation Syndrome.
Approximately 50 cases have been documented since the
syndrome was first described in 1974.
X-linked recessive inheritance (affects
males). The severity of symptoms varies from patient to patient. Some
females (“carriers”) present with some characteristics of FG syndrome, but
they are not affected by the disorder itself. Gene map loci are Xq28,
Xq12-q21.31, and Xp22.3.
Neuropathology findings are suggestive of a
diffuse defect of neuronal cell migration.
Mainly clinical. The presence of subtle facial anomalies
and the characteristic behavior in mid-childhood facilitate the diagnosis,
as does the presence of other affected male relatives in the maternal
family. Usually, the child presenting with the disease has a friendly,
loquacious hyperactive behavior, with occasional aggressive outbursts.
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.
If a cardiac defect is suspected,
obtain an ECG and an echocardiogram before surgery. Ensure the patient
does not have a respiratory infection that tends to be recurrent in these patients as a result
of the hypotonia.
Neuromuscular relaxants are probably
best avoided or used in a reduced dose because of the presence of hypotonia.
Some patients have a narrow palate and mild micrognathia, making direct
laryngoscopy and tracheal intubation difficult. Joint contractures require a
careful positioning in the operating room.
In the presence of a cardiac defect,
antibioprophylaxis may be required.
Graham JM Jr, Superneau D, Rogers RC, et al: Clinical and behavioral
characteristics in FG syndrome. Am J Med Genet
Graham JM Jr, Tackels D, Dibbern K, et al: FG syndrome: Report of three new
families with linkage to Xq12-q22.1. Am J Med Genet
Ozonoff S, Williams BJ, Rauch AM, et al: Behavior phenotype of FG syndrome:
Cognition, personality, and behavior in eleven affected boys. Am J Med Genet 97:112-8,