The most common areas of the brain which give rise to gelastic seizures are the hypothalamus (a small but extremely important structure deep in the centre of the brain), the temporal lobes and the frontal lobes. If the child has gelastic seizures and precocious puberty, then it is likely that the child will be found to have a hypothalamic hamartoma (a hamartoma in the hypothalamus part of the brain). Genetics
This condition is very rare; its prevalence is unknown. Mutations in the GLI3 gene cause Pallister–Hall syndrome. The GLI3 gene provides instructions for making a protein that controls gene expression, which is a process that regulates whether genes are turned on or off in particular cells. By interacting with certain genes at specific times during development, the GLI3 protein plays a role in the normal shaping (patterning) of many organs and tissues before birth. Defects in the same gene also cause Greig cephalopolysyndactyly syndrome. Mutations that cause Pallister–Hall syndrome typically lead to the production of an abnormally short version of the GLI3 protein. Unlike the normal GLI3 protein, which can turn target genes on or off, the short protein can only turn off (repress) target genes. Researchers are working to determine how this change in the proteins function affects early development. It remains uncertain how GLI3 mutations can cause polydactyly, hypothalamic hamartoma, and the other features of Pallister–Hall syndrome. This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
In some cases, an affected person inherits a mutation in the GLI3 gene from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family. Diagnosis
Treatment
Notable Cases
George William Helon (Australian author and businessman) is a Pallister-Hall Syndrome (PHS) patient, mentor, counsellor and advocate. References
Pallister–Hall syndrome at NLM Genetics Home Reference

External links

GeneReviews/NCBI/NIH/UW entry on Pallister–Hall Syndrome
Genetics Home Reference