SERUM AND URINARY AMINO-ACID LEVELS IN SICKLE-CELL DISEASE

Neonates with sickle cell disease (SCD) are of normal size at birth in terms of height and weight. However, by the sixth month of life their growth begins to lag significantly behind that of non-sicklers. We hy pothesize that such growth retardation could be explained, at least in part, by the increased excretion of free amino acids in the urine of children with SCD. It is well established that in SCD there are abnorm alities in the proximal tubules where amino acids are reabsorbed. We c ollected serum and urine samples from 13 patients with SCD (age range, 10 months to 14 years), and 17 age- and gender-matched controls, and analysed these specimens for free amino acids and creatinine. The SCD population was less well nourished than the controls, as evidenced by the lower serum prealbumin levels in the former group (91.3 v. 127 mg/ l, P = 0.01). The serum concentrations of all of the essential amino a cids were significantly reduced (21-47 per cent, P < 0.01) in the SCD subjects, as were those of most of the non essential amino acids (exce ptions: alanine, glutamic acid, proline). The urine concentrations of seven of the essential amino acids (indexed to creatinine) were increa sed in the SCD children. The greatest difference in urinary amino acid excretion was seen with methionine; the SCD subjects excreted 3.6-fol d more methionine than the controls. These data Indicate that reduced levels of serum amino acids resulting from increased urinary loss of t hese amino acids in children with SCD could contribute to the decrease d growth rates one sees in children with this genetically inherited he matologic disorder.