EVALUATION OF ANEMIA IN CYSTINOSIS

Abstract

Cystinosis is a metabolic disorder with deposition of cystine in various organs, including kidneys and bone marrow (BM). Slowly progressive renal failure is due to renal tubular dysfunction and glomerulosclerosis. Normocytic, normochromic anemia is usually present in later stages. We have studied 2 brothers, ages 8 and 5 years, with cystinosis and anemia with 59Fe to measure the amount and effectiveness of erythropoiesis. The 8-year-old had a Hb of 5.5 g/dl with 4% reticulocytes, mildly decreased plasma iron clearance (PIC), normal iron utilization (FeU), and plasma iron turnover (PIT) at the lower limits of normal. There was delayed appearance of 59Fe on BM scan, but normal distribution of marrow reticulo-endothelial elements, measured by 99mtechnetium. Serum and urine erythropoietin levels were inappropriately low for the degree of anemia. Renal function values were BUN 59 mg%, creatinine (C) 6.9 mg%, and creatinine clearance (CC) 10.7 ml/min/1.73M2. The 5-year-old had Hb of 9 g/dl with 0.6% reticulocytes, and normal PIC, PIT, and FeU. Renal function values were BUN 41 mg%, C 1.8 Mg%, and CC 43.7 ml/min/1.73M2. The normal FeU and normal or nearly normal PIC indicate that the BM is capable of utilizing iron to produce red cells which survive to circulate. In the older patient, however, the PIT is at the lower limit of normal despite marked anemia, suggesting no compensatory increase in red cell production. These findings are similar to those in other renal disease and do not indicate a defect specific to cystinosis.