Clinical Utility of Urinary N-Acetyl-β-D-Glucosaminidase (NAG), Kidney Injury Molecule-1 (KIM-1), and Diffusion-Weighted Renal MRI for the Early Detection of Sickle Cell Nephropathy in Children

Sickle cell disease was the first condition to be understood as a molecular disease, as described by Pauling and colleagues in 1949, and later helped to elucidate principles of gene expression, haemoglobin switching, and globin gene regulation.

Sickle cell disease refers to a group of inherited red blood cell (RBC) disorders caused by pathogenic variants in the HBB gene, resulting in the production of sickle haemoglobin S (HbS). Individuals with one copy of the mutation have sickle cell trait a condition that confers partial protection against severe malaria while those with pathogenic variants on both alleles develop the clinical syndrome of sickle cell disease.

The defining pathophysiological mechanism of sickle cell disease is the polymerization of deoxygenated HbS, leading to red cell sickling, haemolysis, and vaso-occlusion accompanied by a cascade of complex pathophysiological events. This cascade drives the multisystem complications of the disease, including acute painful crisis, acute chest syndrome, stroke and cognitive impairment, and progressive organ damage.

Sickle nephropathy often begins in childhood with impaired urine concentrating ability and glomerular hyperfiltration, eventually progressing to albuminuria, reduced glomerular filtration rate, and end-stage renal disease.

Up to one-third of adults with sickle cell disease develop overt proteinuria or decreased glomerular filtration rate, and kidney dysfunction is independently associated with early mortality. Hydroxyurea and angiotensin-converting enzyme inhibitors remain first-line therapies for reducing albuminuria and slowing progression.