Hyperkalaemia in a tetraplegic adolescent due to de novo sodium channel mutation

Maintenance of potassium homeostasis is crucial for the survival of humans and other mammals. In general, potassium levels result from the relationship between potassium intake, urinary potassium excretion and the distribution of potassium between the intracellular and extracellular space. In healthy subjects, potassium excesses are primarily buffered by rapid cell uptake. In a second step, excessive serum potassium is then largely balanced via potassium excretion in the urine, mediated by the renal cortical collecting tubules. These cellular and urinary adaptations normally prevent significant potassium accumulation in the extracellular fluid. Hyperkalaemia is defined as a condition in which serum potassium levels exceed concentrations of 5.0–5.5 mmol/l. Nephrologists usually have to deal with hyperkalaemia on a daily basis and the causes thereof are indeed numerous. However, they can be assigned to four major categories: (i) excessive K + -intake and tissue necrosis, (ii) reduced renal K + -excretion, (iii) redistribution of internal K + via K + -shift and (iv) pseudohyperkalaemia. Hyperkalaemia primarily affects skeletal muscles and the heart, resulting in typical clinical symptoms such as weakness, paralysis and palpitations [ 1 ]. Depending on interindividual susceptibility and the extent of hyperkalaemia, classical ECG changes such as ‘peaked T waves’ or ‘broadened QRS’ can develop, and in extreme cases even culminate in sudden cardiac arrest and death [ 2 ]. Renal specialists are often consulted for help in managing hyperkalaemic patients, but in some cases, the ‘renal trace’ can be misleading in unravelling the true root cause of the problem.