Screening for variants in TPMT did not reduce the proportions of patients with hematologic ADRs during thiopurine treatment for IBD. However, there was a 10-fold reduction in hematologic ADRs among variant carriers who were identified and received a dose reduction, compared with variant carriers who did not, without differences in treatment efficacy. ClinicalTrials.gov number: NCT00521950.

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Life-threatening situations of hyperkalaemia are often caused by renal failure, hyperglycaemia or medication. However pseudohyperkalaemia, a falsely elevated potassium concentration, is usually caused by haemolysis, repeated clenching of the fist during venepuncture or abnormal cell numbers. Another rare cause of pseudohyperkalaemia is familial pseudohyperkalaemia, an autosomal dominantly inherited trait, with increased leakage of potassium from erythrocytes. Under normal in vivo conditions, this increased leakage is compensated by augmented activity of the Na(+)/K(+) ATPase pump. However, after venepuncture the blood cools down to room temperature, reducing the activity of the Na(+)/K(+) ATPase pump whereby the increased potassium leakage becomes more apparent. Here, we present a Dutch patient with extreme familial pseudohyperkalaemia. Interestingly, his two children also show increased potassium leakage at room temperature, albeit at a lower level. Despite the low prevalence of familial pseudohyperkalaemia, it can have important clinical implications and rapid recognition is desired.

Background and Aim of This Study. Itch frequently occurs in patients with chronic cholestasis. However, it remains unclear why some patients do and others do not develop pruritus. In addition, drug treatment is frequently ineffective. We repeatedly observed that cholestatic patients without itch had a relatively high serum gamma-glutamyl transpeptidase (GGT), relative to their serum bilirubin. The aim of this study was to validate this clinical observation. Methods. We included 235 patients with chronic extrahepatic cholestasis due to pancreatic cancer, cholangiocarcinoma, or papillary carcinoma. Results. GGT was significantly higher in patients without pruritus (median 967, IQR 587–1571) compared to patients with pruritus (median 561 IQR 266–1084 IU/l) ( p < 0.01 ). In contrast, median alkaline phosphatase (AP) was 491 U/L (IQR; 353–684) in patients with pruritus and was not significantly different from 518 U/L (IQR; 353–726) in patients without pruritus ( p = 0.524 ). Direct bilirubin was significantly higher in patients with pruritus compared to patients without pruritus (168 μmol/L (IQR; 95–256) vs. 120 μmol/L (IQR; 56.75–185.5)) ( p < 0.01 ). After correcting for the extent of cholestasis via direct bilirubin, the negative association between GGT and pruritus remained significant and became stronger ( p < 0.001 ). Conclusion. Serum GGT activity is inversely associated with the presence of cholestatic itch in patients with chronic extrahepatic cholestasis.