This is a severe form of hereditary neurologic disease, one of several somewhat similar disorders accompanied by facial dysmorphism and failure to develop normally as the result of a delay in psychomotor development.
The characteristic facial features may be mild and not evident at birth. However, infants are 'floppy' at birth and their reflexes are decreased. It soon becomes evident that these children are not developing normally as their milestones are delayed. Many never sit, stand, or walk. Speech is delayed and some children never learn to speak. There is considerable variation in the severity of symptoms so that some individuals may be able to walk and can live into adulthood. The eyes appear deeply-set and there may be abnormal eye movements and poor focusing on targets.
Brain imaging has revealed a lack of normal brain development throughout different areas. The skull is shortened but the forehead is prominent. The nose appears small while the mouth is large and the upper lip is narrow.
Cognitive deficits are common and some authors make the diagnosis of mental retardation.
This is an autosomal recessive disorder in which both members of a specific pair of genes are changed (mutated). The parents with one copy seem to develop normally but when both have a single copy of the mutation, there is a 25% risk that each of their children will inherit the two changes and develop this condition.
When the facial features are sufficiently characteristic the diagnosis may be suspected at birth but if not the parents may note failure to develop normal motor and mental skills. Floppiness can also be a diagnostic sign from birth. Pediatricians and neurologists are likely to collaborate in the diagnosis which will usually require advanced brain imaging and gene studies for confirmation.
No treatment for the condition is available. Some children die during childhood but others can live to adulthood. Special education and physical rehabilitation may benefit some individuals.