Teaching Case

A 7 month old female was referred to our hospital for evaluation of polydactyly.

A 7 months old female was referred to our hospital for evaluation of polydactyly. She was a product of Caesarean-section at 39 weeks with no significant antenatal history. She was gaining weight normally with normal milestones. On physical examination, fused supernumerary digits were found on the ulnar side of left hand. Review of other systems was normal. Radiograph of hands revealed Y-shaped fusion of 3rd and 4th metacarpals with thin distal phalanx of thumb on right side. On the left side, there is Y-shaped fusion of 3rd and 4th metacarpals with rudimentary metacarpal and phalanges on the ulnar side of 4th metacarpal consistent polydactyly. Abnormally thin distal phalanx of left thumb is also seen. MRI brain revealed MR showed T1 and T2 isointense, homogenous, solid mass in the region of hypothalamus without enhancement consistent with hypothalamic hamartoma. On direct laryngoscopy, bifid epiglottis was found. All these findings led to diagnosis of Pallister-hall syndrome.

Hypothalamic hamartoma associated with mesoaxial polydactyly (Fig.1) and bifid epiglottis are characteristic features of Pallister-Hall syndrome.
This syndrome was first described by Hall, Pallister and colleagues in 1980 with a description of hypothalamic hamartoblastoma, hypopituitarism, imperforate anus and postaxial polydactyly [1]. It is inherited in an autosomal dominant fashion with variable expressivity [2]. Mutation in the GL13 gene on the chromosome 7 is associated with this syndrome [3].
Hypothalamic hamartoma also known as tuber cinereum hamartoma is typically noncalcified, isointense on T1 (Fig.2) and hypo to hyperintense on T2 (Fig.3) weighted images without contrast enhancement (Fig. 4) [4]. A patient with hypothalamic hamartoma is usually asymptomatic and surgical removal is not indicated as it can cause pituitary insufficiency. Occasionally it can also cause intractable seizures known as gelastic seizures. Other differential diagnoses considered in the suprasellar region are craniopharyngioma which is a cystic tumour and hypothalamic/ chiasmatic glioma which usually shows enhancement.
Postaxial polydactyly is the presence of extra digits on the ulnar or fibular aspect of limb. The most striking changes are usually found around the fourth finger [1]. Short 4th metacarpal and small underdeveloped fingers are usual features [1]. Central or mesoaxial polydactyly is the presence of six or more well formed digits with a ‘Y’ shaped metacarpal or metatarsal bone. Mesoaxial polydactyly is seen in Pallister-Hall syndrome but probably less common than postaxial polydactyly [5].
Midfacial defect is another is another characteristic feature of this syndrome and bifid epiglottis is most often observed. In a study conducted by Ondrey et al, bifid or cleft epiglottis was found in 15 (58%) out of 26 subjects with Pallister-Hall syndrome [6]. Other features of Pallister-Hall syndrome are renal anomalies and imperforate anus.
Other polydactyly syndrome includes Oral- facial- digital syndrome type VI (insertional polydactyly, hamartomas of the tongue), Smith-Lemli-Opitz syndrome (polydactyly with holoprosencephaly), and Mckusick- Kaufmann syndrome (polydactyly and hydrometrocolpos) [7]. The hypothalamic hamartoma is the key feature in differentiating Pallister-Hall syndrome from these syndromes.
In summary, diagnosis of Pallister-Hall syndrome is made on clinical and family history with imaging findings. Imaging plays a key role in the diagnosis demonstrating hypothalamic hamartoma, polydactyly and shortening of metacarpals and phalanges. Proper diagnosis can avoid unnecessary surgical removal of hypothalamic mass and leads to proper genetic counselling.