Immune checkpoint inhibitors, such as the receptor programmed cell death protein 1 (PD-1) or PD-1 ligand 1 (PD-L1), which are new therapeutic weapons against cancer, which are increasingly used nowadays.

This case report concerns a 72-year-old man treated by pembrolizumab (Keytruda®), a PD-1 inhibitor, in first-line systemic treatment of an Stage IVA lung adenocarcinoma. Three weeks before his eighth cure, the patient’s general condition deteriorated, including loss of appetite, fatigue, nausea, and a slight weigh loss. He also reported headaches. As an adrenal insufficiency was suspected, a substitution treatment consisting of hydrocortisone was initiated. The originality of this case lies in the relevance of also considering non-specific symptoms in cancer patients under immunotherapy, the emergency of the diagnosis, and the recommended medical management.

The aim of this article is direct your attention to this rare but potentially fatal adverse event of immunotherapy, with its new treatments that you will encounter increasingly often in your practice, and to revise some cases already published in the literature , in addition to another personal case.

Introduction. Hypokalemia is often discovered accidentally during routine check-ups. In some cases, however, it may be accompanied by severe symptoms like rhabdomyolysis, potentially leading to life-threatening cardiac rhythm disturbances.

Clinical case. We report the case of a 60-year-old woman admitted to the emergency department with marked anorexia, general weakness, diarrhea, and abdominal pain, which had progressively worsened over the last few weeks. Initial blood analyses showed hypokalemia (1.44mmol/L) as well as rhabdomyolysis (CK 6561 U/L). The cause of her condition could not be identified based on etiological investigations, whereas thorough history taking revealed massive chronic ingestion of cola (10 liters a day).

Discussion. The consumption of high quantities of cola can lead to hypokalemia through the effects of caffeine, glucose, and fructose. Caffeine induces severe hypokalemia by two mechanisms: intracellular redistribution of potassium and increased renal excretion of potassium. Additionally, substances with high fructose content cause osmotic diarrhea with secondary hypokalemia. The high glucose concentration in cola also induces hyperinsulinism, which is associated with intracellular redistribution of potassium.

Conclusion. Chronic and massive consumption of cola can lead to hypokalemia through intracellular potassium shifts, along with osmotic diarrhea caused by high fructose concentrations. Primary care physicians should inquire about soda consumption among their patients when confronted with unexplained cases of refractory hypokalemia.