Purpose or Case Report: Pallister-Hall syndrome is an exceedingly rare genetic disorder characterized by multiorgan anomalies encompassing hypothalamic hamartoma, postaxial polydactyly, bifid epiglottis, renal malformations and imperforate anus. The syndrome arises from a mutation in the GLI3 gene, which can be inherited in autosomal dominant fashion or occur de novo. A significant manifestation of Pallister-Hall syndrome is the presence of a hypothalamic hamartoma, a benign tumor of the hypothalamus. Although benign, these lesions can cause severe endocrine dysfunction by interfering with the hypothalamic-pituitary axis. Abnormal neural or glial cell migration in the tuber cinereum of the hypothalamus leads to abnormal expansion of the hypothalamus, manifesting in a spectrum of pituitary dysfunction ranging from pituitary displacement to severe pan-hypopituitarism. A well-established feature of the hypothalamic hamartomas associated with Pallister-Hall syndrome is the incidence of gelastic seizures (so-called “laughing” seizures), characterized by episodes of involuntary laughing.

A male neonate was born with polydactyly, bifid epiglottis, cryptorchidism, and Hirschsprung’s disease. The patient was additionally found to have right sided vesicouteral reflux requiring extravesical ureteral reimplantation. Genetic analysis revealed a mutation in the GLI3 gene, compatible with Pallister-Hall syndrome. Once diagnosed, the patient underwent contrast-enhanced MR imaging of the brain which demonstrated a large lobulated 2.6 x 2.0 cm suprasellar mass with encroachment posteriorly upon the midbrain and associated superior displacement of the third ventricle. The lesion showed low-grade enhancement following gadolinium contrast administration, displayed no significant abnormality on diffusion-weighted or susceptibility weighted imaging, and was isodense to brain tissue on all sequences. Serial follow-up MRIs demonstrated minimal increase in size of the non-enhancing suprasellar mass. Findings were suggestive of hypothalamic hamartoma, in keeping with the classical presentation of Pallister-Hall syndrome.
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