Background: Congenital hyperinsulinism is the most common cause of persistent hypoglycaemia in early infancy. Mutations in the HNF4A gene lead to transient hyperinsulinism in early infancy and maturity-onset diabetes of youth (MODY1), later in life. Fanconi syndrome is a generalised dysfunction of the renal proximal tubule with a loss of glucose, amino acids, phosphate, low molecular weight proteins, bicarbonate and urate, causing growth failure and rickets in childhood.
Case reports: Patient 1: full-term female infant with normal birth weight presented with recurrent neonatal hypoglycaemia and hypoglycaemic convulsions because of hyperinsulinism. Therapy with diazoxid was necessary for the first 6 months of life. At 3 years of age, an atypical renal Fanconi syndrome with bilateral nephrocalcinosis was diagnosed. The child had radiological and clinical signs of phosphopenic rickets. Therapy with calcitriol and cholecaliferol as well as supplementation with oral sodium phosphate led to regression of the rachitic malformation. Mutational analysis revealed a heterozygous HNF4A R76W (c.187C>Tp.R63W) mutation. Patient 2: pre-term, large-for-gestational age male infant presented with severe recurrent neonatal hypoglycaemia because of hyperinsulinism. Hypoglycaemia responded to diazoxid therapy. In addition, the child developed a Fanconi syndrome at 5 months of age. Radiological evidence was present for rickets. Therapy with calcitriol and supplementation with oral sodium phosphate and sodium bicarbonate was started. However, the patient failed to thrive and was below the 3rd percentile for both weight and length at 6 months of age. The result of mutational analysis will be presented.
Conclusion: The clinical presentation of transient neonatal hyperinsulinism and renal Fanconi syndrome suggests the presence of an inactivating mutation in HNF4A. This disease entity seems to be a further differential diagnosis of congenital hyperinsulinism.
01 Oct 2015 - 03 Oct 2015