Autosomal dominant hemolytic uremic syndrome: variable phenotypes and transplant results

Autosomal dominant hemolytic uremic syndrome (ADHUS) is a rare disorder with a poor prognosis that was considered to present mainly in adults. Recurrent episodes of ADHUS were also thought to be uncommon. However, increasing reports suggest that children are often affected, that recurrent episodes may occur pretransplantation, and that post-transplant recurrences occur in about 50% of cases. We describe the occurrence of ADHUS in two unrelated families with different outcomes. It is apparent that there are several types of ADHUS (with and without serum complement abnormalities) and that there may be variable expression of the phenotype. There was variable penetration of HUS in four (possibly five) adults and two children in four generations of one kindred. There was also one definite unaffected carrier. Two patients had successful renal transplants without recurrences; the HUS recurred in a third patient soon after transplantation. In a second family, the father had three episodes of HUS at 18, 26 and 29 years of age; his son had one episode of HUS at 5 years of age. Both recovered completely. Evaluation of these patients, previous reports, and follow-up contacts of previous reports suggests that post-transplant recurrence of ADHUS is more common than previously reported and may not be prevented by prior nephrectomy of native kidneys.

Discrepancies in pediatric bone mineral density reference data: potential for misdiagnosis of osteopenia

OBJECTIVE

To evaluate published pediatric dual-energy x-ray absorptiometry bone mineral density (BMD) reference data by comparing the diagnostic classification of measured BMD in children at risk for osteopenia as healthy or osteopenic according to reference source.

STUDY DESIGN

Spine BMD was measured in 95 children, ages 9 to 15 years, at risk for osteopenia because of childhood disease. The BMD results were converted to age-specific z scores for each of the 5 reference data sets, and the z -score distributions were compared.

RESULTS

Between 11% and 30% of children were classified as osteopenic (z score < -2.0) depending on the reference data set. The 2 sex-specific reference data sets yielded similar diagnostic classification of boys and girls: 10% of boys and 11% to 16% of girls were osteopenic (P =.4). The 3 sex-nonspecific reference data sets classified 9% to 13% of girls and 24% to 44% of boys as osteopenic; the diagnosis of osteopenia was significantly greater in boys (P <.01).

CONCLUSIONS

The use of different published reference data for the assessment of children at risk for osteopenia results in inconsistent diagnostic classification of BMD results. These inconsistencies can be partially attributed to sex-nonspecific reference data that result in misclassification of boys as osteopenic.

Evaluation of low density spine software for the assessment of bone mineral density in children

Pediatric dual-energy X-ray absorptiometry spine scans often cannot be analyzed with standard software due to a failure to identify the bone edges of low density vertebrae. Low density spine (LDS) software improves bone detection compared with standard software. The objective of this study was to compare bone mineral density (BMD) measurements obtained with the standard and LDS software in 27 healthy nonobese, 32 obese, and 41 chronically ill children, ages 2-18 years. Lumbar spine (L1-L4) BMD, measured by standard analysis, ranged from 0.531-1.244 gm/cm2. Reanalysis with the LDS software resulted in a systematic increase (mean +/- SD) in estimated bone area of 17.0+/-5.0%, an increase in bone mineral content of 6.1+/-6.3%, and a mean decrease in BMD of 8.7+/-1.7% (all p < 0.001). This resulted in a mean decrease in BMD Z score of 0.7+/-0.2. Linear regression models, predicting standard BMD from LDS BMD, were fit for the three subject groups (R2 = 0.993-0.995). Small differences in slopes were detected across groups (p = 0.07); LDS BMD predicted higher standard BMD in obese subjects. In conclusion, LDS analysis resulted in a clinically significant decrease in measured BMD. The association between analysis methods was exceptionally high (R2 > 0.99), indicating that LDS BMD accurately predicts standard BMD. Although LDS BMD in obese subjects predicts higher standard BMD results than in nonobese subjects, the small difference is of questionable clinical significance. LDS software is a useful tool for the assessment of BMD in children.

Incorrect diagnosis of diabetes mellitus in a patient with persistence of fetal haemoglobin

A 65-year-old woman, referred to the endocrine clinic for investigation of tiredness and arthritis, was diagnosed as having diabetes on the basis of a positive family history and a raised glycated haemoglobin (HbA1) measurement. Subsequently, she was shown not to have diabetes but to have a persistently raised haemoglobin F (HbF) level. Initial assessment of HbF level by electroendosmosis demonstrated a normal HbF level but high values were confirmed using HPLC. Thalassaemia was excluded following DNA analysis. This case illustrates the importance of a glucose tolerance test following WHO criteria for the diagnosis of diabetes and emphasises that HbA1 is not a diagnostic test for diabetes.

Interaction between tacrolimus and chloramphenicol in a renal transplant recipient

BACKGROUND

The metabolism of tacrolimus is influenced by several medications when they are given concurrently. We report the interaction between tacrolimus and chloramphenicol in a renal transplant recipient.

METHODS

An adolescent with vancomycin-resistant Enterococcus was given standard doses of chloramphenicol. Tacrolimus trough levels increased, and the dose was adjusted to maintain the target trough level. Pharmacokinetic studies were obtained during chloramphenicol administration and 14 days after its discontinuation.

RESULTS

Toxic levels of tacrolimus were seen on the second day of chloramphenicol administration, requiring an 83% reduction in the tacrolimus dose. The dose-adjusted area under the curve value for tacrolimus was 7.5-fold greater while the patient was on chloramphenicol. These data are consistent with inhibition of tacrolimus clearance by chloramphenicol

CONCLUSIONS

Chloramphenicol interferes with tacrolimus metabolism. Careful monitoring of tacrolimus trough levels during concomitant chloramphenicol therapy is recommended to avoid toxicity.

Plasma zinc status, growth, and maturation in children with sickle cell disease

OBJECTIVE

The objective of this study was to determine the relation of plasma zinc (Zn) status to growth and maturation in children with SS genotype sickle cell disease.

STUDY DESIGN

A cross-sectional study of 104 subjects who were 50% female and ranged in age from 0.4 to 18 years was performed. Measures included plasma Zn concentration (Znp), height, weight, skinfold thicknesses, elbow breadth, upper arm muscle area, and fat-free mass and fat mass by total body electrical conductivity. Skeletal maturation was assessed by hand-wrist x-ray evaluation and sexual maturation by Tanner stage.

RESULTS

A total of 44% of the patients had low Znp (<10.7 micromol/L [70 microg/dl]); those with low Znp had significantly lower SD scores for height (p = 0.003), weight (p = 0.003), upper arm muscle area (p = 0.045), fat-free mass (p = 0.025), and elbow breadth (p = 0.017) and greater skeletal maturation delay (p = 0.04). In older children (>9 years) low Znp was associated with decreased Tanner scores for pubic hair (p = 0.001) and breast and genital maturation (p = 0.009). No significant differences were seen in age, sex, or fat stores according to Zn status.

CONCLUSIONS

Decreased plasma Zn is common in children with SS genotype sickle cell disease and is associated with decreased linear growth, skeletal growth, muscle mass, and sexual and skeletal maturation.

Effects of the enantiomers of R,S-salbutamol on incompletely fused tetanic contractions of slow- and fast-twitch skeletal muscles of the guinea-pig

1. The effects of racemic R,S-salbutamol, and its individual enantiomers have been studied on incompletely fused (sub-tetanic) contractile responses of fast- and slow-contracting isolated skeletal muscles of the guinea-pig. 2. R,S-salbutamol (2-4 microM) decreased the peak force of sub-tetani in the slow-contracting soleus muscle and increased the peak force of sub-tetani in the fast-contracting peroneus longus muscle. It also increased the force of the first twitch of sub-tetani in both muscles. The decrease in the peak force of sub-tetani in the soleus muscle was due to defusion of the individual twitches caused by a shortening of their time course. 3. The effects of 4 microM of the racemate on both fast- and slow-contracting muscles were mimicked by 2 microM R-salbutamol (levalbuterol). However, 2 microM S-salbutamol was devoid of activity in both muscles. 4. We concluded that all the effects of R,S-salbutamol on guinea-pig skeletal muscles are due to the activity of the R-enantiomer. Thus there is a common enantiomeric profile for the skeletal muscle and bronchorelaxant activity of the compound.

Helicobacter pylori does not release cysteamine into gastric juice

AIM

To determine whether Helicobacter pylori releases cysteamine into gastric juice as cysteamine is known to be ulcerogenic.

METHODS

Samples of fasting gastric juice were collected from 22 individuals (four women); 10 subjects were H pylori negative. The presence of infection was confirmed by examination and culture of gastric biopsies. Cysteamine in gastric juice was measured by reversed phase gradient high performance liquid chromatography with a detection limit of 10 mumol/l.

RESULTS

Cysteamine was not detected in any of the gastric juice samples or in extracts of cultured H pylori.

CONCLUSIONS

If H pylori produces cysteamine then the amounts produced are insignificant and are unlikely to explain the association between H pylori infection and the development of duodenal ulcer disease.

An incidental finding of Gitelman's syndrome

Gitelman's syndrome is characterised by hypokalaemia, hypomagnesaemia and tetany. This rare disorder is not well described in the literature, probably due to its similarity with Bartter's syndrome. We describe the symptoms and treatment of a young patient whom we consider to have Gitelman's syndrome.

A quality assessment scheme for blood glucose monitoring: competition improves performance

Quality assurance procedures are often ignored or forgotten about by wards involved in the blood glucose monitoring of patients. We have devised a complete quality assurance scheme for checking the ward performance of 38 B-M Reflolux meters and two B-M Accutrend meters. Quality control (QC) material, supplied commercially and distributed by the laboratory, is analysed and recorded daily by the wards (internal QC). In addition, a 'spiked', whole blood sample is prepared by the laboratory and distributed for analysis to all wards at six-monthly intervals (external QC). The laboratory also conducts a monthly survey of meter operation (quality assessment) based on a 'scoring system' that allows easy identification of poor performers. Poor performers are counselled accordingly and, if poor performance is persistent, their meter is removed. In our experience, the publication and distribution of ward quality assessment scores has increased competition between wards in terms of avoiding low scores, dramatically improved performance, and ultimately led to improved patient care.

Free radical activity in young adult cigarette smokers

Cigarette smoke is capable of generating free radicals. In this study markers of free radical activity (thiobarbituric acid reactivity, superoxide dismutase and glutathione peroxidase) were measured in young adult smoking and non-smoking volunteers. No significant differences were found in any of the free radical markers between the two groups. The number of leucocytes was elevated and a positive correlation was found between the number of leucocytes and thiobarbituric acid reactivity in the smokers. The results from this study suggest that any free radical activity generated from long term cigarette smoking in young adults is adequately scavenged.

Cigarette smoking and free radical activity in young adults with insulin-dependent diabetes

Cigarette smoke is potentially capable of generating a high free radical load in the body and many patients with diabetes are smokers. This study was designed to investigate the relationship between long-term smoking and free radical activity in young adult insulin-dependent diabetic patients with no evidence of macrovascular disease. Eight-five patients (48 male) aged 17-40 years were studied. Mean duration of diabetes was 10.5 years (0.08-33) and 39 were cigarette smokers. All had normal serum creatinine levels. The free radical markers measured were: thiobarbituric acid reactive substances, glutathione peroxidase, and superoxide dismutase. No significant differences in thiobarbituric acid reactive substances, glutathione peroxidase, or superoxide dismutase, were found between the diabetic smokers and non-smokers. Also no difference was found comparing the diabetic patients with 40 non-diabetic control subjects (20 smokers). Persistent albuminuria was present in 16 patients (10 microalbuminuria) and free radical marker concentrations in these subjects were similar to the normoalbuminuric patients. This data suggests that any increase in free radical activity due to cigarette smoke is adequately scavenged in young adults with diabetes who are free of significant macrovascular disease.

Continuous parenteral infusion of vitamin E pharmacokinetics and bilirubin production in premature neonates

We conclude that 5 mg/kg of vitamin E, administered intra-arterially as an 8-hour continuous infusion, significantly and predictably raises serum vitamin E levels into the supraphysiologic range with no apparent side effects. In a group of premature infants whose initial serum vitamin E levels were generally greater than or equal to 0.5 mg/dL, no decrease in bilirubin production was observed. Thus, vitamin E deficiency probably does not play a prominent role in jaundice of prematurity.

Vancomycin pharmacokinetics in very low birth weight neonates

The pharmacokinetics of vancomycin hydrochloride was studied in 12 very low birth weight infants. The gestational age (mean +/- SD) was 25.9 +/- 1.3 weeks and body weight was 769.2 +/- 151.5 g at the time of initiation of the study. Vancomycin was infused over a period of 60 minutes in a dosage of 14.2 +/- 3.2 mg/kg once daily in 10 patients, twice daily in 1 patient and every 36 hours in 1 patient for a mean of 10.5 +/- 4.9 days. Serial blood samples were obtained and the concentration time data were fitted to a one-compartment open model using the ADAPT computer program. A significant positive correlation was found between postconceptional age and vancomycin clearance (P less than 0.005) and between vancomycin elimination half-life and plasma creatinine (P less than 0.01). A negative correlation existed between plasma creatinine and vancomycin clearance (P less than 0.005), between postconceptional age and plasma creatinine (P less than 0.005) and between vancomycin half-life and postconceptional age (P less than 0.01). On the basis of these findings a vancomycin dosage of 15 mg/kg every 24 hours for infants less than 1000 g should yield concentrations within the accepted therapeutic range. This susceptible population requires frequent monitoring of vancomycin concentrations because of the high degree of interpatient variability and the continuous maturation of renal function.

Interpreting the carboxyhaemoglobin concentration in fetal cord blood

We calculated the fetal-to-maternal carboxyhaemoglobin concentration ratio in 19 mother-infant pairs at the time of term delivery. Mothers, who had a less than 10% drop in their carboxyhaemoglobin concentration during labour, had an average ratio of 1.40 +/- 0.19. For mothers whose carboxyhaemoglobin concentrations dropped by 10% or more during labour, the average fetal-to-maternal carboxyhaemoglobin concentration ratio was 1.83 +/- 0.48. There was a strong correlation (r = 0.82) between the percent change in maternal carboxyhaemoglobin concentration during labour and the fetal-to-maternal carboxyhaemoglobin concentration ratio at the time of delivery. We conclude that increased CO elimination during labour may be accompanied by rapid changes in the maternal carboxyhaemoglobin concentration, leading to a spuriously high fetal-to-maternal carboxyhemoglobin concentration ratio at the time of delivery.

Psoas abscess: changing patterns of diagnosis and etiology

From 1976 to 1984, 43 patients with psoas abscess were seen at the Mayo Clinic. Intestinal disease, including Crohn's disease, diverticulitis, and carcinoma, was the most frequent cause (14 patients). Eleven patients had osteomyelitis, five had postoperative complications, four had a foreign-body reaction, and three had a primary staphylococcal abscess. Two patients each had extension of a primary pancreatic and perinephric abscess. One patient had tuberculosis of the spine, and in the remaining patient, an exact cause was not determined. Definitive treatment of psoas abscess includes adequate debridement, drainage of the abscess cavity, and resection of involved bowel.

The effects of sorbinil on peripheral nerve conduction velocity, polyol concentrations and morphology in the streptozotocin-diabetic rat

This study examined the effects of an aldose reductase inhibitor, Sorbinil, on neuropathy over a 6-month period in streptozotocin-diabetic rats. Sorbinil treatment prevented the 10-fold increase in nerve sorbitol found with diabetes. It produced a 60% improvement in tibial nerve motor conduction velocity after 6 months. Morphometric profiles of nerves were also normalized. Axon area was reduced by 14% in untreated diabetic rats compared to age-matched controls, whereas Sorbinil-treated animals showed normal age-related axon growth. Myelin area was increased by 28% in untreated diabetic animals, but was the same as age-matched controls with Sorbinil treatment. Nerve myo-inositol levels were reduced by 45% after three months of untreated diabetes, but were normal after six months. Sorbinil treatment tended to restore myo-inositol levels toward normal over the shorter time period. It was concluded that axon growth retardation is the most likely cause of the conduction deficit seen in long-term experimental diabetes.