The coincidence of two rare diseases with opposite metabolic phenotype: a child with congenital hyperinsulinism and Bloom syndrome

Abstract

Objectives: Congenital hyperinsulinism (CHI) is a group of rare genetic disorders characterized by insulin overproduction. CHI causes life-threatening hypoglycemia in neonates and infants. Bloom syndrome is a rare autosomal recessive disorder caused by mutations in the BLM gene resulting in genetic instability and an elevated rate of spontaneous sister chromatid exchanges. It leads to insulin resistance, early-onset diabetes, dyslipidemia, growth delay, immune deficiency and cancer predisposition. Recent studies demonstrate that the BLM gene is highly expressed in pancreatic islet cells and its mutations can alter the expression of other genes which are associated with apoptosis control and cell proliferation.

Case presentation: A 5-month-old female patient from consanguineous parents presented with drug-resistant CHI and dysmorphic features. Genetic testing revealed a homozygous mutation in the KCNJ11 gene and an additional homozygous mutation in the BLM gene. While ¹⁸F-DOPA PET scan images were consistent with a focal CHI form and intraoperative frozen-section histopathology was consistent with diffuse CHI form, postoperative histopathological examination revealed features of an atypical form.

Conclusions: In our case, the patient carries two distinct diseases with opposite metabolic phenotypes.

Keywords: Bloom syndrome; congenital hyperinsulinism; hypoglycemia.