Tubular Acidification Defect in Adults with Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Metabolic acidosis is a frequent manifestation of sickle cell disease but the mechanisms and determinants of this disorder are unknown. Our aim was to characterize urinary acidification capacity in adults with sickle cell disease and to identify potential factors associated with decreased capacity to acidify urine.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 25 adults with sickle cell disease and an eGFR of ≥60 ml/min per 1.73 m² from a single center in France, we performed an acute acidification test after simultaneous administration of furosemide and fludrocortisone. A normal response was defined as a decrease in urinary pH <5.3 and an increase in urinary ammonium excretion ≥33 µEq/min at one or more of the six time points after furosemide and fludrocortisone administration.

RESULTS

Of the participants (median [interquartile range] age of 36 [24-43] years old, 17 women), 12 had a normal and 13 had an abnormal response to the test. Among these 13 participants, nine had normal baseline plasma bicarbonate concentration. Plasma aldosterone was within the normal range for all 13 participants with an abnormal response, making the diagnosis of type 4 tubular acidosis unlikely. The participants with an abnormal response to the test were significantly older, more frequently treated with oral bicarbonate, had a higher plasma uric acid concentration, higher hemolysis activity, lower eGFR, lower baseline plasma bicarbonate concentration, higher urine pH, lower urine ammonium ion excretion, and lower fasting urine osmolality than those with a normal response. Considering both groups, the maximum urinary ammonium ion excretion was positively correlated with fasting urine osmolality (r ²=0.34, P=0.002), suggesting that participants with sickle cell disease and lower urine concentration capacity have lower urine acidification capacity.

CONCLUSIONS

Among adults with sickle cell disease, impaired urinary acidification capacity attributable to distal tubular dysfunction is common and associated with the severity of hyposthenuria.

PODCAST

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Three-Year Outcomes of a Randomized, Double-Blind, Placebo-Controlled Study Assessing Safety and Efficacy of C1 Esterase Inhibitor for Prevention of Delayed Graft Function in Deceased Donor Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

Delayed graft function is related to ischemia-reperfusion injury and may be complement dependent. We previously reported from a randomized, placebo-controlled trial that treatment with C1 esterase inhibitor was associated with a shorter duration of delayed graft function and higher eGFR at 1 year. Here, we report longer-term outcomes from this trial.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is a post hoc analysis of a phase 1/2, randomized, controlled trial enrolling 70 recipients of deceased donor kidney transplants at risk for delayed graft function (NCT02134314). Subjects were randomized to receive C1 esterase inhibitor 50 U/kg (n=35) or placebo (n=35) intraoperatively and at 24 hours. The cumulative incidence functions method was used to compare graft failure and death over 3.5 years. eGFR slopes were compared using a linear mixed effects model.

RESULTS

Three deaths occurred among C1 esterase inhibitor-treated patients compared with none receiving placebo. Seven graft failures developed in the placebo group compared with one among C1 esterase inhibitor-treated recipients; the cumulative incidence of graft failure was lower over 3.5 years among C1 esterase inhibitor-treated recipients compared with placebo (P=0.03). Although no difference in eGFR slopes was observed between groups (P for group-time interaction =0.12), eGFR declined in placebo-treated recipients (-4 ml/min per 1.73 m² per year; 95% confidence interval, -8 to -0.1) but was stable in C1 esterase inhibitor-treated patients (eGFR slope: 0.5 ml/min per 1.73 m² per year; 95% confidence interval, -4 to 5). At 3.5 years, eGFR was 56 ml/min per 1.73 m² (95% confidence interval, 42 to 70) in the C1 esterase inhibitor group versus 35 ml/min per 1.73 m² (95% confidence interval, 21 to 48) in the placebo group, with an estimated mean eGFR difference of 21 ml/min per 1.73 m² (95% confidence interval, 2 to 41 ml/min per 1.73 m²).

CONCLUSIONS

Treatment of patients at risk for ischemia-reperfusion injury and delayed graft function with C1 esterase inhibitor was associated with a lower incidence of graft failure.

Metastasizing Maxillary Ameloblastoma: Report of a Case with Molecular Characterization

BACKGROUND

Ameloblastoma is a benign odontogenic tumour that may exhibit aggressive biological behaviour with local recurrence and metastasis following initial surgical resection. Surgery is the most acceptable modality of treatment, even if a biological approach is currently on study. We report a case of maxillary ameloblastoma with development of neck and brain metastases after repeated local recurrences. Molecular analysis was performed with the aim to better characterize this neoplasm and its peculiar behaviour.

METHODS

We investigated the status of tumour protein p53 (TP53), epidermal growth factor receptor (EGFR), B-Raf proto-oncogene (BRAF) and human epidermal growth factor receptor 2 (HER2) genes with immunohistochemical, fluorescent in situ hybridization and/or direct sequencing in order to clarify their possible role in the development of this neoplasm and the possibility of a targeted treatment.

RESULTS

The histological appearance of the tumour was the same in the primary lesion, in the recurrence and in the metastases. EGFR positivity was present in the recurrence and the brain metastasis, while HER2 was negative in all samples tested. Fluorescent in situ hybridization analysis for EGFR showed disomy of neoplastic cells. Direct DNA sequencing of TP53 gene exons 5 - 9 was carried out in tumour samples from the infratemporal recurrence and brain metastasis, with no mutational alteration detected. Similarly, sequencing analysis of BRAF exon 15 (V600) and EGFR gene showed wild type results in all samples tested.

CONCLUSIONS

Further studies are needed to identify molecular pathways that may provide an opportunity of alternative treatments and/or new potential predictive markers of local and distant spread of this rare tumour.