The main signs and symptoms of Opitz-Kaveggia/FG affect male infants and include hypotonia (reduced muscle tone) with global developmental delay and subsequent learning disability; imperforate or narrowed anus (skin covered or blocked bottom) or severe constipation; high prominent forehead with larger than average head circumference and somewhat widened and flattened-appearing thumbs and great toes. Brain scan may show a lesion called agenesis of the corpus callosum that is not in itself harmful. As the imperforate anus is not present in each case and constipation is a non-specific sign, Opitz-Kaveggia/FG can be hard to diagnose and it may therefore have gone unrecognised in the past.
As mentioned above, the clinical features of FG syndrome can vary in different affected individuals and can include:
- learning disability in males
- imperforate anus or severe constipation
- reduced or lax muscle tone in childhood; increased tone in adulthood
- minor changes in appearance such as high broad forehead with upsweep of the hairline (cow's lick), wide-apart eyes, smallish external ears, broad thumbs and great toes
- congenital heart defect (see entry, Heart Defects)
- short stature (see entry Restricted Growth)
- seizures (see entry Epilepsy)
- hearing loss (see entry Deafness)
- hyperactivity and tantrums (see entry Attention Deficit Hyperactivity disorder)
- friendly or out-going personality.