Congenital hyperinsulinism in children with paternal 11p uniparental isodisomy and Beckwith-Wiedemann syndrome.

Background: Congenital hyperinsulinism (HI) can have monogenic or syndromic causes. Although HI has long been recognised to be common in children with Beckwith-Wiedemann syndrome (BWS), the underlying mechanism is not known.

Methods: We characterised the clinical features of children with both HI and BWS/11p overgrowth spectrum, evaluated the contribution of KATP channel mutations to the molecular pathogenesis of their HI and assessed molecular pathogenesis associated with features of BWS.

Results: We identified 28 children with HI and BWS/11p overgrowth from 1997 to 2014. Mosaic paternal uniparental isodisomy for chromosome 11p (pUPD11p) was noted in 26/28 cases. Most were refractory to diazoxide treatment and half required subtotal pancreatectomies. Patients displayed a wide range of clinical features from classical BWS to only mild hemihypertrophy (11p overgrowth spectrum). Four of the cases had a paternally transmitted KATP mutation and had a much more severe HI course than patients with pUPD11p alone.

Conclusions: We found that patients with pUPD11p-associated HI have a persistent and severe HI phenotype compared with transient hypoglycaemia of BWS/11p overgrowth patients caused by other aetiologies. Testing for pUPD11p should be considered in all patients with persistent congenital HI, especially for those without an identified HI gene mutation.