Megan Rodney¹, Jenny Butler², Chris Florkowski¹, Simon Thompson¹, Richard King¹, Kelly Rankin¹

¹Canterbury Health Laboratories, Christchurch, NZ

²Department of General Medicine, Christchurch Hospital, Christchurch, NZ

 

A fit and well 47-year-old woman experienced two years of intermittent hyperkalaemia with no obvious underlying cause. Her highest recorded potassium was 8.9 mmol/L (3.5 – 5.2 mmol/L). During this time, she had been asymptomatic with no electrocardiogram (ECG) evidence of hyperkalaemia. She had been referred acutely to the general medicine department on multiple occasions due to hyperkalaemia, but these episodes resolved without treatment.

 

Hyperkalaemia can be a life-threatening condition therefore it is important to treat promptly¹. It is crucial to be certain the hyperkalaemia is authentic and not due to a pre-analytical cause to avoid spurious treatment, as hypokalaemia is also life-threatening. After ruling out the more common causes of hyperkalaemia, the above patient was investigated for familial pseudohyperkalaemia (FP), a benign autosomal dominant condition due to mutations in the ABCB6 gene¹. It results in impairment of passive sodium and potassium permeability in red blood cells which is a temperature dependent ex-vivo phenomenon². Both time and temperature dependent effects with significant potassium ‘leakage’ from red blood cells were observed in the patient compared to the control, supportive of the diagnosis of FP². The patient was found to be heterozygous for a pathogenic variant in ABCB6 c. 1123C>T³. 

 

 

1. Saleh-Anaraki K, Jain A, Wilcox CS, Pourafshar N. Pseudohyperkalemia: Three Cases and a Review of Literature. The American Journal of Medicine [Internet]. 2022 Jul 1;135(7):e150–4. Available from: https://pubmed.ncbi.nlm.nih.gov/35398330/

2. Xiong W, Song J, Yue Z, Pei L, Liu Y, Chen J, et al. Case Report: Familial Pseudohyperkalemia Due to Red Blood Cell Membrane Leak in a Chinese Patient. Frontiers in Medicine. 2022 Mar 17;9.

3. Andolfo I, Alper SL, Delaunay J, Auriemma C, Russo R, Asci R, et al. Missense mutations in the ABCB6 transporter cause dominant familial pseudohyperkalemia. American Journal of Hematology. 2012 Nov 24;88(1):66–72.