A thirteen-year-old girl was referred to our facility for assessment due to nephrocalcinosis discovered accidentally. Upon physical examination, she was found to have anemia, with normal blood pressure. She had previously been evaluated elsewhere for anemia and received intravenous iron injections for iron deficiency anemia. Subsequently, she had been taking oral iron supplements until recently. The rest of her physical examination and family history were unremarkable.
Further investigation for nephrocalcinosis revealed normal renal function and serum calcium levels, but she exhibited hypophosphatemia. Her iPTH levels were measured at 32 pg/mL, and arterial blood gases were within normal range. Metabolic analysis was conducted using a 24-hour urine sample, revealing hypercalciuria, hyperuricosuria, and reduced tubular reabsorption of phosphorus. Screening for aminoaciduria yielded negative results, and her oral glucose tolerance test was within normal limits. A 24-hour urine protein test showed levels of 278 mg, and her urine culture was sterile. Acid loading test, conducted with ammonium chloride to exclude renal tubular acidosis, indicated normal urinary acidification. An abdominal computerized tomographic scan identified nephrocalcinosis and mild splenomegaly.
The investigation into anemia was prompted by the presence of mild splenomegaly and nephrocalcinosis. Subsequent examinations revealed anemia, characterized by a hemoglobin level of 9.6 gm/dL and a packed cell volume (PCV) of 30%, alongside normal white cell and platelet counts. Analysis of the peripheral smear indicated microcytic hypochromic anemia with a few target cells. Red cell indices showed a mean corpuscular volume (MCV) of 66.1 fl, mean corpuscular hemoglobin (MCH) of 16.7 pg, and mean corpuscular hemoglobin concentration (MCHC) of 26.8. Additionally, the lactate dehydrogenase (LDH) level was measured at 583 IU/L, with a reticulocyte count of 2.0%, and the sickling test yielded negative results. Serum levels of vitamin B12, folate, 25-OH vitamin D3, and 1, 25-OH vitamin D3 were within normal range. Serological tests for ANA, ANCA, anti ds DNA, anti RO, anti LA, and anti u1 RNP returned negative results. The bone marrow findings indicated erythroid hyperplasia. Both direct and indirect Coombs tests yielded negative results. Her iron profile revealed a serum iron level of 90 µg/dL, total iron binding capacity of 224 µg/dL, transferrin saturation of 41.6%, and serum ferritin of 286 ng/mL.
Diagnostic test was done
Renal tubular dysfunction & nephrocalcinosis in patients with beta-thalassemia minor
Patients with betathalassemia minor usually are asymptomatic. Beta-thalassemia minor is characterized by both microcytosis and hypochromia. It requires no treatment.
A variety of renal tubular abnormalities including hypercalciuria, hypomagnesemia with renal magnesium wasting, decreased tubular absorption of phosphorus, hypouricemia with renal uric acid wasting, renal glycosuria and tubular proteinuria have been described even in patients with beta thalassemia minor.
It has been postulated that low-grade hemolysis, shortened red cell life span, tubular iron deposition, oxidative lipid peroxidation and toxins derived from erythrocytes might cause renal tubular damage in patients with beta-thalassemia minor.