Pallister-Hall syndrome

Last revised by Henry Knipe on 19 Nov 2019

Pallister-Hall syndrome displays a wide range of severity and is characterized by hypothalamic hamartomas seen as a mass at the floor of the third ventricle, posterior to the optic chiasm 3,4.

Pallister-Hall syndrome is rare and the exact prevalence is unknown. Patients with postaxial polydactyly and asymptomatic hypothalamic hamartomas or bifid epiglottis may be misdiagnosed as having non-syndromic postaxial polydactyly type A 4.

There is a heterozygous genetic mutation in GLI3 located on chromosome 7p14.1 which is a zinc finger transcriptional activator protein 3,4. On histology, there are disordered arrangements of hyperplastic neurons admixed with astrocytes and minimal white matter which shows varying degrees of myelination 3.

Craniofacial abnormalities are thought to be a result of disruption of the midline development by the hypothalamic hamartoma 3.

MRI is the imaging modality of choice for hypothalamic hamartoma. They appear as non-calcified, non-enhancing and homogeneously isointense to grey matter on T1 weighted images and often hyperintense on T2 weighted images 3. These findings are helpful in distinguishing hypothalmic hamartoma from more common suprasellar lesions such as craniopharyngioma 3.

Prognosis in those with no known family history is based on the severity of the malformations present. The early lethality phenotype is likely associated with panhypopituitarism, severe airway malformation such as laryngotracheal clefts and / or unrecognised imperforate anus 4.

The following conditions contain overlapping clinical features 3:

  • Ellis-van Crevald syndrome
  • Smith-Lemil-Opitz syndrome
  • oral-facial-digital syndrome type IV
  • Kaufman-McKusick syndrome
  • Greig cephalosyndactyly syndrome

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