Lysosomal Enzymuria in Protein Energy Malnutrition

Abstract

Protein energy malnutrition (PEM) is common in underprivileged populations in many parts of the world and results from diets deficient in protein (kwashiorkor) or protein and calories (marasmus). The literature documents renal tubular abnormalities in children with PEM. In PEM the reabsorption of amino acids and phosphate is defective. In many kidney disorders in which renal tubular function is impaired (e.g., diabetes, preeclampsia, nephrotic syndrome, sickle cell anemia), lysosomal enzymuria ensues. We compared the urinary excretion of the following five lysosomal enzymes in 31 Nigerian children with marasmus, kwashiorkor, or marasmic-kwashiorkor: β-hexosaminidase, α-galactosidase, β-galactosidase, β-glucuronidase, and α-mannosidase. All of the protein energy malnourished children and the 18 age- and gender-matched controls were from the city of Jos, located in central Nigeria. In the severely malnourished children, the urine levels of all five lysosomal enzymes (expressed as units of enzyme activity per mg creatinine) were markedly increased. The greatest increases were seen with β-hexosaminidase (16-fold) and β-glucuronidase (14-fold). Routine clinical analyses also revealed that, relative to the control population, the sera of the 14 most severely malnourished patients contained 2- to 5-fold more vitamin B₁₂ and markedly reduced levels (15%, p < 0.00001) of calcium. These data are significant in that they document lysosomal enzymuria in Nigerian children with severe PEM and point to the potential diagnostic utility of the urinary β-galactosidase determination for assessing renal function in children with this disorder.