Exocrine pancreatic insufficiency as an unusual extrarenal manifestation of proximal renal tubular acidosis associated with a novel SLC4A4 mutation

Autosomal recessive proximal renal tubular acidosis (AR-pRTA) with ocular abnormalities is a rare syndrome caused by variants in the SLC4A4 gene, which encodes Na/HCO3 cotransporter (NBCe1). The syndrome primarily affects the kidneys, but also causes extra-renal manifestations. Pancreatic type NBCe1 is located at the basolateral membrane of the pancreatic ductal cells and together with CFTR chloride channel, it is involved in bicarbonate secretion. In vitro models have demonstrated that mutations in the pancreatic type NBCe1 lead to a reduction in pancreatic bicarbonate secretion. Although elevated amylase levels have been observed in some cases, there is no evidence of symptomatic pancreas involvement in children with AR-pRTA. This report presents the case of a seven-year-old girl with AR-pRTA and exocrine pancreatic insufficiency. This novel presentation with a novel mutation in SLC4A4 expands the extra-renal involvement in this rare disease. We recommend that these children be screened for exocrine pancreatic insufficiency.