Tetany in a child with AIDS receiving intravenous tobramycin

Aminoglycosides have been reported to cause tetany by inducing renal wasting of magnesium and secondary hypocalcemia. A 9-year-old girl with AIDS was brought to the emergency department because of tetany. She had just finished a 3-week course of intravenous tobramycin for bronchiectasis and had an elevated serum tobramycin trough level 1 week before the onset of tetany. Hypomagnesemia, hypokalemia, and hypocalcemia had developed. The urine revealed inappropriately high levels of magnesium and potassium despite critically low serum levels, with an appropriately low urine calcium level. This pattern is suggestive of renal toxicity due to tobramycin. Over the next several months, she continued to require supplemental calcium, magnesium, potassium, and phosphorus. She also had nephrotic range proteinuria. Aminoglycoside renal mineral wasting has not previously been described in a child.

Hyponatremia in pediatric patients with HIV-1 infection

Hyponatremia has been recognized as a complication in adults with acquired immunodeficiency syndrome (AIDS). We did a retrospective study evaluating the medical records of 86 children (age 4 months to 21 years) with human immunodeficiency virus (HIV-1) infection to determine the frequency and clinical associations of hyponatremia. Twenty-two children (26%) developed hyponatremia (serum sodium < 135 mEq/L; range 104 to 134 mEq/L; mean 130 mEq/L). Fourteen were male; 18 of the 22 patients were black and 4 were white. At the time of hyponatremia, the children frequently had comorbid associations, including 8 (35%) with AIDS encephalopathy; 3 (14%) with cardiomyopathy; 3 (14%) using diuretics; 1 (5%) using pentamidine; 3 (14%) with bacterial pneumonia; 2 (9%) requiring gastric lavage feedings; 2 (9%) with tuberculosis meningitis; 2 (9%) with gastroenteritis; 1 (5%) with infection caused by Mycobacterium avium-intracellulare; 1 (5%) each with brain tumor and tumor metastasis to brain. The cause of hyponatremia was attributed to syndrome of inappropriate antidiuretic hormone in 8 children; poor sodium intake and/or excessive diarrheal losses in 5; and the use of diuretics in 3 patients. Mild hyponatremia with no identifiable cause was found in 5 patients.

Increased antibody responsiveness to blood transfusions in pediatric patients

Heightened immune responsiveness has been proposed as one of the reasons underlying suboptimal renal transplant results in very young children or African American recipients. Because multiple factors influence graft outcome, it has been difficult to provide experimental evidence to confirm or refute this suggestion. In the present study we measured IgG antibodies with confirmed HLA specificity produced in response to blood transfusions. The patients evaluated were renal transplant candidates who had not had previous pregnancies or transplants. The overall incidence of HLA sensitization was 12%. Age was the most influential factor in sensitization: patients < 20 years old were 4-5 times as likely to produce anti-HLA antibodies than patients > 20 (P = 0.0018). Female patients were also high responders. However, this was explained by the higher proportion of children among nulliparous female patients rather than by differences in gender. In contrast, the antibody response of black and white recipients was similar. The antibody levels in most patients were low and decreased significantly with time. We conclude that the immunoregulatory influences in patients < 20 years old favor the production of anti-HLA antibodies in response to blood transfusions, a fact that may explain some clinical observations in pediatric transplant recipients.

Idiopathic Fanconi syndrome in a family. Part I. Clinical aspects

Fanconi syndrome is a rare cause of rickets in children. Only six families with Fanconi syndrome following an autosomal dominant pattern of inheritance have been reported. In this report, the results of clinical studies performed in three generations of a family of 39 members with autosomal dominant Fanconi syndrome are presented. Twenty-one members of this family provided blood and urine for biochemical evaluation. Many family members have one or more tubular reabsorptive abnormalities; however, the complete Fanconi syndrome was not present in most members. Three children with the complete syndrome all occur in the last generation. When the characteristic features of this family were compared with those of previously reported families with autosomal dominant Fanconi syndrome, several differences became apparent. Two serious manifestations, diabetes mellitus and renal failure, which occur in previous reports did not occur in this family. This report provides information on apparently the largest number of affected individuals in a single family with Fanconi syndrome. In addition, variable expressivity of tubular reabsorptive defects in a family with Fanconi syndrome has never been reported.

NMR measurements of intra- and extravesicular sodium in renal microvilli

Previous attempts to separate the nuclear magnetic resonances of intra- and extravesicular Na+ in brush-border membrane vesicles (BBMV) were unsuccessful and led to the proposal of rapid exchange of Na+ via sodium channels in BBMV. However, passive conductance of Na+ in this membrane has been found to be relatively small. This inconsistency prompted us to use a different shift reagent to reassess the issue. In guinea pig renal BBMV (15-30 mg protein/ml) equilibrated with Na+ (130 mequiv. 1), using the impermeant Na+ shift reagent dysprosium tripolyphosphate (3 mM), the resonances of intra- (3.3%) and extravesicular (96.7%) Na+ were resolved by 6 ppm. Increases in Na+ conductance induced by gramicidin D did not alter the characteristics of intra- and extravesicular Na+ resonances. By contrast, addition of glucose caused a transient increase in the area of the intravesicular Na+ resonance. The clear separation between the intra- and the extravesicular Na+ resonances allowed us to measure the relaxation times of Na+, which depend on its interactions with its immediate environment. The longitudinal relaxation time of intravesicular Na+ (13 +/- 1 ms) was much shorter than that of the extravesicular Na+ (44.0 +/- 0.4 ms). Thus, in intact renal BBMV, as well as in membranes treated with the cationophore gramicidin D, the exchange of Na+ between the intra- and the extravesicular compartments is slow on the NMR time scale, consistent with the low Na+ channel density of this membrane. In contrast, the increase in intravesicular Na+ induced by glucose, is consistent with a significant contribution of the glucose cotransport pathway to Na+ flux across these membranes. The short longitudinal relaxation time of Na+ in the intravesicular space indicates interaction of Na+ with BBMV binding sites or ordering of these ions in the intravesicular compartment.